diff --git a/ChangeLog b/ChangeLog
index f6b4cef56cf6..fe5ba17610ab 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -19,6 +19,9 @@ Security
      DTLS client when parsing the Hello Verify Request message.
 
 Bugfix
+   * Add missing limits.h standard C library header to ssl_tls.c and udp_proxy.c
+     which was only including it via check_config.h previously, which may not be
+     included in custom configuration files. Fixes #1803
    * Fix compilation failure when both MBEDTLS_SSL_PROTO_DTLS and
      MBEDTLS_SSL_HW_RECORD_ACCEL are enabled.
    * Fix a function name in a debug message. Contributed by Ercan Ozturk in
diff --git a/configs/config-ccm-psk-tls1_2.h b/configs/config-ccm-psk-tls1_2.h
index a783e6b73b80..8519686f1941 100644
--- a/configs/config-ccm-psk-tls1_2.h
+++ b/configs/config-ccm-psk-tls1_2.h
@@ -83,6 +83,4 @@
  */
 #define MBEDTLS_SSL_MAX_CONTENT_LEN             512
 
-#include "mbedtls/check_config.h"
-
 #endif /* MBEDTLS_CONFIG_H */
diff --git a/configs/config-mini-tls1_1.h b/configs/config-mini-tls1_1.h
index 013bc0300d5e..d6764d3006ab 100644
--- a/configs/config-mini-tls1_1.h
+++ b/configs/config-mini-tls1_1.h
@@ -73,6 +73,4 @@
 /* For testing with compat.sh */
 #define MBEDTLS_FS_IO
 
-#include "mbedtls/check_config.h"
-
 #endif /* MBEDTLS_CONFIG_H */
diff --git a/configs/config-no-entropy.h b/configs/config-no-entropy.h
index b4a0930b9c02..31a7368f6801 100644
--- a/configs/config-no-entropy.h
+++ b/configs/config-no-entropy.h
@@ -86,6 +86,4 @@
 /* Miscellaneous options */
 #define MBEDTLS_AES_ROM_TABLES
 
-#include "check_config.h"
-
 #endif /* MBEDTLS_CONFIG_H */
diff --git a/configs/config-suite-b.h b/configs/config-suite-b.h
index 18e2c4036995..09fcd01dd272 100644
--- a/configs/config-suite-b.h
+++ b/configs/config-suite-b.h
@@ -112,6 +112,4 @@
  */
 #define MBEDTLS_SSL_MAX_CONTENT_LEN             1024
 
-#include "mbedtls/check_config.h"
-
 #endif /* MBEDTLS_CONFIG_H */
diff --git a/configs/config-thread.h b/configs/config-thread.h
index 25db16bf0f84..1671c62af9bf 100644
--- a/configs/config-thread.h
+++ b/configs/config-thread.h
@@ -89,6 +89,4 @@
 /* Save ROM and a few bytes of RAM by specifying our own ciphersuite list */
 #define MBEDTLS_SSL_CIPHERSUITES MBEDTLS_TLS_ECJPAKE_WITH_AES_128_CCM_8
 
-#include "mbedtls/check_config.h"
-
 #endif /* MBEDTLS_CONFIG_H */
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 0bc08cca4463..ba1ee7e9b7d2 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -2871,6 +2871,4 @@
 #include MBEDTLS_USER_CONFIG_FILE
 #endif
 
-#include "check_config.h"
-
 #endif /* MBEDTLS_CONFIG_H */
diff --git a/library/aes.c b/library/aes.c
index beeecae370cf..81e8dc430f6d 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -30,6 +30,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_AES_C)
 
diff --git a/library/aesni.c b/library/aesni.c
index 1ca3c3ef5b9a..b274092e31a8 100644
--- a/library/aesni.c
+++ b/library/aesni.c
@@ -29,6 +29,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_AESNI_C)
 
diff --git a/library/arc4.c b/library/arc4.c
index 05b33d3fdbb9..56573a21f2d4 100644
--- a/library/arc4.c
+++ b/library/arc4.c
@@ -29,6 +29,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_ARC4_C)
 
diff --git a/library/asn1parse.c b/library/asn1parse.c
index 4dd65c03c029..11206321d769 100644
--- a/library/asn1parse.c
+++ b/library/asn1parse.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_ASN1_PARSE_C)
 
diff --git a/library/asn1write.c b/library/asn1write.c
index b451887ed39e..e3c9c2289676 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_ASN1_WRITE_C)
 
diff --git a/library/base64.c b/library/base64.c
index f06b57b31fcd..e8818ded0b8c 100644
--- a/library/base64.c
+++ b/library/base64.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_BASE64_C)
 
diff --git a/library/bignum.c b/library/bignum.c
index 827a3cb669ad..358242cabdde 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -40,6 +40,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_BIGNUM_C)
 
diff --git a/library/blowfish.c b/library/blowfish.c
index 9003f0dfeb28..aed95e6c0525 100644
--- a/library/blowfish.c
+++ b/library/blowfish.c
@@ -30,6 +30,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_BLOWFISH_C)
 
diff --git a/library/camellia.c b/library/camellia.c
index ac6f96a83a30..80bd9e43902d 100644
--- a/library/camellia.c
+++ b/library/camellia.c
@@ -30,6 +30,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_CAMELLIA_C)
 
diff --git a/library/ccm.c b/library/ccm.c
index 658f0d2ff37e..08dd63aead9b 100644
--- a/library/ccm.c
+++ b/library/ccm.c
@@ -33,6 +33,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_CCM_C)
 
diff --git a/library/certs.c b/library/certs.c
index 7cc71ae83995..cd70967cb050 100644
--- a/library/certs.c
+++ b/library/certs.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #include "mbedtls/certs.h"
 
diff --git a/library/cipher.c b/library/cipher.c
index b4101823c436..7942288d5918 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -28,6 +28,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_CIPHER_C)
 
diff --git a/library/cipher_wrap.c b/library/cipher_wrap.c
index dbc5d3fe4826..f57de9908127 100644
--- a/library/cipher_wrap.c
+++ b/library/cipher_wrap.c
@@ -28,6 +28,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_CIPHER_C)
 
diff --git a/library/cmac.c b/library/cmac.c
index 9a73faa6d5c5..296a55c8134d 100644
--- a/library/cmac.c
+++ b/library/cmac.c
@@ -45,6 +45,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_CMAC_C)
 
diff --git a/library/ctr_drbg.c b/library/ctr_drbg.c
index 0638354317da..3faf2805f329 100644
--- a/library/ctr_drbg.c
+++ b/library/ctr_drbg.c
@@ -29,6 +29,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_CTR_DRBG_C)
 
diff --git a/library/debug.c b/library/debug.c
index 30c8c7bb81be..78edc348aa3c 100644
--- a/library/debug.c
+++ b/library/debug.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_DEBUG_C)
 
diff --git a/library/des.c b/library/des.c
index 09f95cfc3b38..8602ea6f7270 100644
--- a/library/des.c
+++ b/library/des.c
@@ -30,6 +30,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_DES_C)
 
diff --git a/library/dhm.c b/library/dhm.c
index 28ac31003c92..74353891378b 100644
--- a/library/dhm.c
+++ b/library/dhm.c
@@ -32,6 +32,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_DHM_C)
 
diff --git a/library/ecdh.c b/library/ecdh.c
index 75630bd35686..5f43ad908093 100644
--- a/library/ecdh.c
+++ b/library/ecdh.c
@@ -31,6 +31,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_ECDH_C)
 
diff --git a/library/ecdsa.c b/library/ecdsa.c
index 24bf73473ee3..8280c5972dd0 100644
--- a/library/ecdsa.c
+++ b/library/ecdsa.c
@@ -30,6 +30,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_ECDSA_C)
 
diff --git a/library/ecjpake.c b/library/ecjpake.c
index 65ba0d081788..0139f1d0fc67 100644
--- a/library/ecjpake.c
+++ b/library/ecjpake.c
@@ -29,6 +29,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_ECJPAKE_C)
 
diff --git a/library/ecp.c b/library/ecp.c
index 108695bf56d8..524b8eeb7043 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -45,6 +45,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_ECP_C)
 
diff --git a/library/ecp_curves.c b/library/ecp_curves.c
index df5ac3eea510..e2388b5856a6 100644
--- a/library/ecp_curves.c
+++ b/library/ecp_curves.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_ECP_C)
 
diff --git a/library/entropy.c b/library/entropy.c
index e17512e779ab..88b8923b2210 100644
--- a/library/entropy.c
+++ b/library/entropy.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_ENTROPY_C)
 
diff --git a/library/entropy_poll.c b/library/entropy_poll.c
index 02b25a272128..e7e025389841 100644
--- a/library/entropy_poll.c
+++ b/library/entropy_poll.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_ENTROPY_C)
 
diff --git a/library/error.c b/library/error.c
index 9445e510e64e..52c8c4f019c7 100644
--- a/library/error.c
+++ b/library/error.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_ERROR_C) || defined(MBEDTLS_ERROR_STRERROR_DUMMY)
 #include "mbedtls/error.h"
diff --git a/library/gcm.c b/library/gcm.c
index 294a86d3d47d..789f755d130d 100644
--- a/library/gcm.c
+++ b/library/gcm.c
@@ -34,6 +34,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_GCM_C)
 
diff --git a/library/havege.c b/library/havege.c
index 69e5c3a41dc1..b7ff7843b495 100644
--- a/library/havege.c
+++ b/library/havege.c
@@ -31,6 +31,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_HAVEGE_C)
 
diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c
index 346c2632107d..69dea3e6da37 100644
--- a/library/hmac_drbg.c
+++ b/library/hmac_drbg.c
@@ -30,6 +30,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_HMAC_DRBG_C)
 
diff --git a/library/md.c b/library/md.c
index 00249af78bcd..aadbd38eee7d 100644
--- a/library/md.c
+++ b/library/md.c
@@ -28,6 +28,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_MD_C)
 
diff --git a/library/md2.c b/library/md2.c
index b88aa406afad..7021ff4980da 100644
--- a/library/md2.c
+++ b/library/md2.c
@@ -30,6 +30,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_MD2_C)
 
diff --git a/library/md4.c b/library/md4.c
index ba704f58e8b9..922c257b822d 100644
--- a/library/md4.c
+++ b/library/md4.c
@@ -30,6 +30,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_MD4_C)
 
diff --git a/library/md5.c b/library/md5.c
index 3ba88cfc5ddc..9adcf1c6cda9 100644
--- a/library/md5.c
+++ b/library/md5.c
@@ -29,6 +29,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_MD5_C)
 
diff --git a/library/md_wrap.c b/library/md_wrap.c
index 32f087197657..84bea9068c03 100644
--- a/library/md_wrap.c
+++ b/library/md_wrap.c
@@ -28,6 +28,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_MD_C)
 
diff --git a/library/memory_buffer_alloc.c b/library/memory_buffer_alloc.c
index eb555f332699..cfc863a32f9a 100644
--- a/library/memory_buffer_alloc.c
+++ b/library/memory_buffer_alloc.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
 #include "mbedtls/memory_buffer_alloc.h"
diff --git a/library/net_sockets.c b/library/net_sockets.c
index c659d3602cb1..65bfb96f01a2 100644
--- a/library/net_sockets.c
+++ b/library/net_sockets.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_NET_C)
 
diff --git a/library/oid.c b/library/oid.c
index edea950f8fab..70c98a8a4192 100644
--- a/library/oid.c
+++ b/library/oid.c
@@ -26,6 +26,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_OID_C)
 
diff --git a/library/padlock.c b/library/padlock.c
index b85ff9cd2c9a..e597b9e69644 100644
--- a/library/padlock.c
+++ b/library/padlock.c
@@ -30,6 +30,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_PADLOCK_C)
 
diff --git a/library/pem.c b/library/pem.c
index ac86d7e4790c..b35ac14ff607 100644
--- a/library/pem.c
+++ b/library/pem.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_PEM_PARSE_C) || defined(MBEDTLS_PEM_WRITE_C)
 
diff --git a/library/pk.c b/library/pk.c
index b52c73fbc69c..140d1e7a79ed 100644
--- a/library/pk.c
+++ b/library/pk.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_PK_C)
 #include "mbedtls/pk.h"
diff --git a/library/pk_wrap.c b/library/pk_wrap.c
index 5446e23507c0..a998ce81f189 100644
--- a/library/pk_wrap.c
+++ b/library/pk_wrap.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_PK_C)
 #include "mbedtls/pk_internal.h"
diff --git a/library/pkcs11.c b/library/pkcs11.c
index 0ea64252ee4f..dc632d6753dc 100644
--- a/library/pkcs11.c
+++ b/library/pkcs11.c
@@ -23,9 +23,15 @@
  *  This file is part of mbed TLS (https://tls.mbed.org)
  */
 
-#include "mbedtls/pkcs11.h"
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_PKCS11_C)
+#include "mbedtls/pkcs11.h"
 
 #include "mbedtls/md.h"
 #include "mbedtls/oid.h"
diff --git a/library/pkcs12.c b/library/pkcs12.c
index 5e8b2879a06b..d490cd188f9f 100644
--- a/library/pkcs12.c
+++ b/library/pkcs12.c
@@ -30,6 +30,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_PKCS12_C)
 
diff --git a/library/pkcs5.c b/library/pkcs5.c
index 50133435ceb7..42fdb2b9ad9e 100644
--- a/library/pkcs5.c
+++ b/library/pkcs5.c
@@ -34,6 +34,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_PKCS5_C)
 
diff --git a/library/pkparse.c b/library/pkparse.c
index 7502fe7ffdc4..302a16cd0f2c 100644
--- a/library/pkparse.c
+++ b/library/pkparse.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_PK_PARSE_C)
 
diff --git a/library/pkwrite.c b/library/pkwrite.c
index fa934703abb3..ca9a657ad4c4 100644
--- a/library/pkwrite.c
+++ b/library/pkwrite.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_PK_WRITE_C)
 
diff --git a/library/platform.c b/library/platform.c
index aa88fc1a664a..7952557dba3c 100644
--- a/library/platform.c
+++ b/library/platform.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_PLATFORM_C)
 
diff --git a/library/ripemd160.c b/library/ripemd160.c
index 2ba48b7fdb7a..541930349f41 100644
--- a/library/ripemd160.c
+++ b/library/ripemd160.c
@@ -30,6 +30,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_RIPEMD160_C)
 
diff --git a/library/rsa.c b/library/rsa.c
index 98c529f00509..1afe405b8734 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -42,6 +42,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_RSA_C)
 
diff --git a/library/rsa_internal.c b/library/rsa_internal.c
index 507009f131f7..1d64f4a47f54 100644
--- a/library/rsa_internal.c
+++ b/library/rsa_internal.c
@@ -25,6 +25,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_RSA_C)
 
diff --git a/library/sha1.c b/library/sha1.c
index 5d0335d5aedb..b40633b16f82 100644
--- a/library/sha1.c
+++ b/library/sha1.c
@@ -29,6 +29,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_SHA1_C)
 
diff --git a/library/sha256.c b/library/sha256.c
index 4ec9164a8d50..8b623de00623 100644
--- a/library/sha256.c
+++ b/library/sha256.c
@@ -29,6 +29,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_SHA256_C)
 
diff --git a/library/sha512.c b/library/sha512.c
index db2617ebdf55..afd7fa671e67 100644
--- a/library/sha512.c
+++ b/library/sha512.c
@@ -29,6 +29,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_SHA512_C)
 
diff --git a/library/ssl_cache.c b/library/ssl_cache.c
index 47867f132d60..b47e0c7e0eca 100644
--- a/library/ssl_cache.c
+++ b/library/ssl_cache.c
@@ -28,6 +28,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_SSL_CACHE_C)
 
diff --git a/library/ssl_ciphersuites.c b/library/ssl_ciphersuites.c
index 01d1c458a24c..60db8185d35e 100644
--- a/library/ssl_ciphersuites.c
+++ b/library/ssl_ciphersuites.c
@@ -26,6 +26,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_SSL_TLS_C)
 
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 07cc5dd3405d..dc67a4ba7496 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_SSL_CLI_C)
 
diff --git a/library/ssl_cookie.c b/library/ssl_cookie.c
index caf119990d5d..5f5644aa1ce5 100644
--- a/library/ssl_cookie.c
+++ b/library/ssl_cookie.c
@@ -28,6 +28,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_SSL_COOKIE_C)
 
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 6f607b440709..97e48485c55d 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_SSL_SRV_C)
 
diff --git a/library/ssl_ticket.c b/library/ssl_ticket.c
index 555c7b63bf95..b0fe83cd4575 100644
--- a/library/ssl_ticket.c
+++ b/library/ssl_ticket.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_SSL_TICKET_C)
 
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 5f6ae6200013..1d62c6ed7760 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -32,6 +32,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_SSL_TLS_C)
 
@@ -47,6 +48,7 @@
 #include "mbedtls/ssl.h"
 #include "mbedtls/ssl_internal.h"
 
+#include <limits.h>
 #include <string.h>
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
diff --git a/library/threading.c b/library/threading.c
index f1c37245c707..b03470ad34b8 100644
--- a/library/threading.c
+++ b/library/threading.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_THREADING_C)
 
diff --git a/library/timing.c b/library/timing.c
index 9ccaf4093113..c1c668b9d684 100644
--- a/library/timing.c
+++ b/library/timing.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
diff --git a/library/version.c b/library/version.c
index 6ca80d469557..e0aab65a2866 100644
--- a/library/version.c
+++ b/library/version.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_VERSION_C)
 
diff --git a/library/version_features.c b/library/version_features.c
index d6deb01498ef..46a6eb25bff4 100644
--- a/library/version_features.c
+++ b/library/version_features.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_VERSION_C)
 
diff --git a/library/x509.c b/library/x509.c
index c12f7fbfe12d..47469edfff64 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -34,6 +34,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_X509_USE_C)
 
diff --git a/library/x509_create.c b/library/x509_create.c
index df20ec8ebd7f..d293083ef009 100644
--- a/library/x509_create.c
+++ b/library/x509_create.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_X509_CREATE_C)
 
diff --git a/library/x509_crl.c b/library/x509_crl.c
index 3ceb77091ee3..d7a40669afda 100644
--- a/library/x509_crl.c
+++ b/library/x509_crl.c
@@ -34,6 +34,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_X509_CRL_PARSE_C)
 
diff --git a/library/x509_crt.c b/library/x509_crt.c
index 762735518c35..45b43d87e78f 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -34,6 +34,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
 
diff --git a/library/x509_csr.c b/library/x509_csr.c
index 87c179e3d4c0..c0678a4320d8 100644
--- a/library/x509_csr.c
+++ b/library/x509_csr.c
@@ -34,6 +34,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_X509_CSR_PARSE_C)
 
diff --git a/library/x509write_crt.c b/library/x509write_crt.c
index 905de4cfa232..5d6b717c9559 100644
--- a/library/x509write_crt.c
+++ b/library/x509write_crt.c
@@ -30,6 +30,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_X509_CRT_WRITE_C)
 
diff --git a/library/x509write_csr.c b/library/x509write_csr.c
index 8582a8b2098a..bf6dc581d3f4 100644
--- a/library/x509write_csr.c
+++ b/library/x509write_csr.c
@@ -29,6 +29,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_X509_CSR_WRITE_C)
 
diff --git a/library/xtea.c b/library/xtea.c
index fe0a3509f6f7..e56ea7ba9bc4 100644
--- a/library/xtea.c
+++ b/library/xtea.c
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_XTEA_C)
 
diff --git a/programs/test/udp_proxy.c b/programs/test/udp_proxy.c
index e0b43517d374..40a2fa651674 100644
--- a/programs/test/udp_proxy.c
+++ b/programs/test/udp_proxy.c
@@ -57,6 +57,7 @@ int main( void )
 #include "mbedtls/error.h"
 #include "mbedtls/ssl.h"
 
+#include <limits.h>
 #include <string.h>
 
 /* For select() */
diff --git a/scripts/data_files/error.fmt b/scripts/data_files/error.fmt
index a08742c83bb7..b5924d05997c 100644
--- a/scripts/data_files/error.fmt
+++ b/scripts/data_files/error.fmt
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_ERROR_C) || defined(MBEDTLS_ERROR_STRERROR_DUMMY)
 #include "mbedtls/error.h"
diff --git a/scripts/data_files/version_features.fmt b/scripts/data_files/version_features.fmt
index 767eda1c7469..37287bd111f5 100644
--- a/scripts/data_files/version_features.fmt
+++ b/scripts/data_files/version_features.fmt
@@ -24,6 +24,7 @@
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
+#include "mbedtls/check_config.h"
 
 #if defined(MBEDTLS_VERSION_C)