diff --git a/functable.c b/functable.c
index c3c3707ee..e068a5e55 100644
--- a/functable.c
+++ b/functable.c
@@ -134,10 +134,11 @@ extern uint32_t longest_match_unaligned_avx2(deflate_state *const s, Pos cur_mat
 #endif
 #endif
 
-Z_INTERNAL Z_TLS struct functable_s functable;
+/* functable init */
+Z_INTERNAL struct functable_s functable;
 
 /* stub functions */
-Z_INTERNAL void insert_string_stub(deflate_state *const s, const uint32_t str, uint32_t count) {
+static void __attribute__((constructor)) insert_string_stub() {
     // Initialize default
 
     functable.insert_string = &insert_string_c;
@@ -149,11 +150,9 @@ Z_INTERNAL void insert_string_stub(deflate_state *const s, const uint32_t str, u
     if (arm_cpu_has_crc32)
         functable.insert_string = &insert_string_acle;
 #endif
-
-    functable.insert_string(s, str, count);
 }
 
-Z_INTERNAL Pos quick_insert_string_stub(deflate_state *const s, const uint32_t str) {
+static void __attribute__((constructor)) quick_insert_string_stub_init() {
     functable.quick_insert_string = &quick_insert_string_c;
 
 #ifdef X86_SSE42_CRC_HASH
@@ -163,11 +162,9 @@ Z_INTERNAL Pos quick_insert_string_stub(deflate_state *const s, const uint32_t s
     if (arm_cpu_has_crc32)
         functable.quick_insert_string = &quick_insert_string_acle;
 #endif
-
-    return functable.quick_insert_string(s, str);
 }
 
-Z_INTERNAL void slide_hash_stub(deflate_state *s) {
+static void __attribute__((constructor)) slide_hash_stub_init() {
 
     functable.slide_hash = &slide_hash_c;
 
@@ -190,11 +187,9 @@ Z_INTERNAL void slide_hash_stub(deflate_state *s) {
     if (power_cpu_has_arch_2_07)
         functable.slide_hash = &slide_hash_power8;
 #endif
-
-    functable.slide_hash(s);
 }
 
-Z_INTERNAL uint32_t adler32_stub(uint32_t adler, const unsigned char *buf, size_t len) {
+static void __attribute__((constructor)) adler32_stub_init() {
     // Initialize default
     functable.adler32 = &adler32_c;
 
@@ -216,11 +211,9 @@ Z_INTERNAL uint32_t adler32_stub(uint32_t adler, const unsigned char *buf, size_
     if (power_cpu_has_arch_2_07)
         functable.adler32 = &adler32_power8;
 #endif
-
-    return functable.adler32(adler, buf, len);
 }
 
-Z_INTERNAL uint32_t chunksize_stub(void) {
+static void __attribute__((constructor)) chunksize_stub_init(void) {
     // Initialize default
     functable.chunksize = &chunksize_c;
 
@@ -238,11 +231,9 @@ Z_INTERNAL uint32_t chunksize_stub(void) {
     if (arm_cpu_has_neon)
         functable.chunksize = &chunksize_neon;
 #endif
-
-    return functable.chunksize();
 }
 
-Z_INTERNAL uint8_t* chunkcopy_stub(uint8_t *out, uint8_t const *from, unsigned len) {
+static void __attribute__((constructor)) chunkcopy_stub_init() {
     // Initialize default
     functable.chunkcopy = &chunkcopy_c;
 
@@ -260,11 +251,9 @@ Z_INTERNAL uint8_t* chunkcopy_stub(uint8_t *out, uint8_t const *from, unsigned l
     if (arm_cpu_has_neon)
         functable.chunkcopy = &chunkcopy_neon;
 #endif
-
-    return functable.chunkcopy(out, from, len);
 }
 
-Z_INTERNAL uint8_t* chunkcopy_safe_stub(uint8_t *out, uint8_t const *from, unsigned len, uint8_t *safe) {
+static void __attribute__((constructor)) chunkcopy_safe_stub_init() {
     // Initialize default
     functable.chunkcopy_safe = &chunkcopy_safe_c;
 
@@ -282,11 +271,9 @@ Z_INTERNAL uint8_t* chunkcopy_safe_stub(uint8_t *out, uint8_t const *from, unsig
     if (arm_cpu_has_neon)
         functable.chunkcopy_safe = &chunkcopy_safe_neon;
 #endif
-
-    return functable.chunkcopy_safe(out, from, len, safe);
 }
 
-Z_INTERNAL uint8_t* chunkunroll_stub(uint8_t *out, unsigned *dist, unsigned *len) {
+static void __attribute__((constructor)) chunkunroll_stub_init() {
     // Initialize default
     functable.chunkunroll = &chunkunroll_c;
 
@@ -305,11 +292,9 @@ Z_INTERNAL uint8_t* chunkunroll_stub(uint8_t *out, unsigned *dist, unsigned *len
     if (arm_cpu_has_neon)
         functable.chunkunroll = &chunkunroll_neon;
 #endif
-
-    return functable.chunkunroll(out, dist, len);
 }
 
-Z_INTERNAL uint8_t* chunkmemset_stub(uint8_t *out, unsigned dist, unsigned len) {
+static void __attribute__((constructor)) chunkmemset_stub_init() {
     // Initialize default
     functable.chunkmemset = &chunkmemset_c;
 
@@ -327,11 +312,9 @@ Z_INTERNAL uint8_t* chunkmemset_stub(uint8_t *out, unsigned dist, unsigned len)
     if (arm_cpu_has_neon)
         functable.chunkmemset = &chunkmemset_neon;
 #endif
-
-    return functable.chunkmemset(out, dist, len);
 }
 
-Z_INTERNAL uint8_t* chunkmemset_safe_stub(uint8_t *out, unsigned dist, unsigned len, unsigned left) {
+static void __attribute__((constructor)) chunkmemset_safe_stub_init() {
     // Initialize default
     functable.chunkmemset_safe = &chunkmemset_safe_c;
 
@@ -349,11 +332,9 @@ Z_INTERNAL uint8_t* chunkmemset_safe_stub(uint8_t *out, unsigned dist, unsigned
     if (arm_cpu_has_neon)
         functable.chunkmemset_safe = &chunkmemset_safe_neon;
 #endif
-
-    return functable.chunkmemset_safe(out, dist, len, left);
 }
 
-Z_INTERNAL uint32_t crc32_stub(uint32_t crc, const unsigned char *buf, uint64_t len) {
+static void __attribute__((constructor)) crc32_stub_init() {
     int32_t use_byfour = sizeof(void *) == sizeof(ptrdiff_t);
 
     Assert(sizeof(uint64_t) >= sizeof(size_t),
@@ -375,11 +356,9 @@ Z_INTERNAL uint32_t crc32_stub(uint32_t crc, const unsigned char *buf, uint64_t
     } else {
         functable.crc32 = crc32_generic;
     }
-
-    return functable.crc32(crc, buf, len);
 }
 
-Z_INTERNAL uint32_t compare258_stub(const unsigned char *src0, const unsigned char *src1) {
+static void __attribute__((constructor)) compare258_stub_init() {
 
     functable.compare258 = &compare258_c;
 
@@ -400,11 +379,9 @@ Z_INTERNAL uint32_t compare258_stub(const unsigned char *src0, const unsigned ch
         functable.compare258 = &compare258_unaligned_avx2;
 #  endif
 #endif
-
-    return functable.compare258(src0, src1);
 }
 
-Z_INTERNAL uint32_t longest_match_stub(deflate_state *const s, Pos cur_match) {
+static void __attribute__((constructor)) longest_match_stub_init() {
 
     functable.longest_match = &longest_match_c;
 
@@ -425,23 +402,4 @@ Z_INTERNAL uint32_t longest_match_stub(deflate_state *const s, Pos cur_match) {
         functable.longest_match = &longest_match_unaligned_avx2;
 #  endif
 #endif
-
-    return functable.longest_match(s, cur_match);
 }
-
-/* functable init */
-Z_INTERNAL Z_TLS struct functable_s functable = {
-    insert_string_stub,
-    quick_insert_string_stub,
-    adler32_stub,
-    crc32_stub,
-    slide_hash_stub,
-    compare258_stub,
-    longest_match_stub,
-    chunksize_stub,
-    chunkcopy_stub,
-    chunkcopy_safe_stub,
-    chunkunroll_stub,
-    chunkmemset_stub,
-    chunkmemset_safe_stub
-};
diff --git a/functable.h b/functable.h
index 276c284a0..efcad1d57 100644
--- a/functable.h
+++ b/functable.h
@@ -24,6 +24,6 @@ struct functable_s {
     uint8_t* (* chunkmemset_safe)   (uint8_t *out, unsigned dist, unsigned len, unsigned left);
 };
 
-Z_INTERNAL extern Z_TLS struct functable_s functable;
+Z_INTERNAL extern struct functable_s functable;
 
 #endif
diff --git a/zutil.h b/zutil.h
index 497cb22b4..64a7e25a0 100644
--- a/zutil.h
+++ b/zutil.h
@@ -24,10 +24,6 @@
 #  define Z_REGISTER
 #endif
 
-#ifndef Z_TLS
-#  define Z_TLS
-#endif
-
 #include <stddef.h>
 #include <string.h>
 #include <stdlib.h>