diff --git a/include/mbedtls/aesni.h b/include/mbedtls/aesni.h
index 0da40a0a3cfb..c9fe2bf35674 100644
--- a/include/mbedtls/aesni.h
+++ b/include/mbedtls/aesni.h
@@ -58,7 +58,7 @@
  *       macros that may change in future releases.
  */
 #undef MBEDTLS_AESNI_HAVE_INTRINSICS
-#if defined(_MSC_VER)
+#if defined(_MSC_VER) && !defined(__clang__)
 /* Visual Studio supports AESNI intrinsics since VS 2008 SP1. We only support
  * VS 2013 and up for other reasons anyway, so no need to check the version. */
 #define MBEDTLS_AESNI_HAVE_INTRINSICS
@@ -66,7 +66,7 @@
 /* GCC-like compilers: currently, we only support intrinsics if the requisite
  * target flag is enabled when building the library (e.g. `gcc -mpclmul -msse2`
  * or `clang -maes -mpclmul`). */
-#if defined(__GNUC__) && defined(__AES__) && defined(__PCLMUL__)
+#if (defined(__GNUC__) || defined(__clang__)) && defined(__AES__) && defined(__PCLMUL__)
 #define MBEDTLS_AESNI_HAVE_INTRINSICS
 #endif
 
diff --git a/library/aesni.c b/library/aesni.c
index 866b6cbfbf10..fee6b02c20dd 100644
--- a/library/aesni.c
+++ b/library/aesni.c
@@ -57,7 +57,7 @@ int mbedtls_aesni_has_support(unsigned int what)
 
     if (!done) {
 #if MBEDTLS_AESNI_HAVE_CODE == 2
-        static unsigned info[4] = { 0, 0, 0, 0 };
+        static int info[4] = { 0, 0, 0, 0 };
 #if defined(_MSC_VER)
         __cpuid(info, 1);
 #else
@@ -191,7 +191,7 @@ void mbedtls_aesni_gcm_mult(unsigned char c[16],
                             const unsigned char a[16],
                             const unsigned char b[16])
 {
-    __m128i aa, bb, cc, dd;
+    __m128i aa = {0}, bb = {0}, cc, dd;
 
     /* The inputs are in big-endian order, so byte-reverse them */
     for (size_t i = 0; i < 16; i++) {