diff --git a/tests/suites/test_suite_ctr_drbg.function b/tests/suites/test_suite_ctr_drbg.function
index d8ffebe46..73f63b976 100644
--- a/tests/suites/test_suite_ctr_drbg.function
+++ b/tests/suites/test_suite_ctr_drbg.function
@@ -1,5 +1,6 @@
 /* BEGIN_HEADER */
 #include "mbedtls/ctr_drbg.h"
+#include "string.h"
 
 static int test_offset_idx;
 static int mbedtls_test_entropy_func( void *data, unsigned char *buf, size_t len )
diff --git a/tests/suites/test_suite_debug.function b/tests/suites/test_suite_debug.function
index 98f98b061..a32eba0c2 100644
--- a/tests/suites/test_suite_debug.function
+++ b/tests/suites/test_suite_debug.function
@@ -1,5 +1,6 @@
 /* BEGIN_HEADER */
 #include "mbedtls/debug.h"
+#include "string.h"
 
 struct buffer_data
 {
diff --git a/tests/suites/test_suite_entropy.function b/tests/suites/test_suite_entropy.function
index 2bab796d1..9930c0386 100644
--- a/tests/suites/test_suite_entropy.function
+++ b/tests/suites/test_suite_entropy.function
@@ -1,6 +1,7 @@
 /* BEGIN_HEADER */
 #include "mbedtls/entropy.h"
 #include "mbedtls/entropy_poll.h"
+#include "string.h"
 
 /*
  * Number of calls made to entropy_dummy_source()
diff --git a/tests/suites/test_suite_hmac_drbg.function b/tests/suites/test_suite_hmac_drbg.function
index a413f5e18..21b300e7c 100644
--- a/tests/suites/test_suite_hmac_drbg.function
+++ b/tests/suites/test_suite_hmac_drbg.function
@@ -1,5 +1,6 @@
 /* BEGIN_HEADER */
 #include "mbedtls/hmac_drbg.h"
+#include "string.h"
 
 typedef struct
 {
diff --git a/tests/suites/test_suite_x509parse.function b/tests/suites/test_suite_x509parse.function
index 06f010828..d02068d5f 100644
--- a/tests/suites/test_suite_x509parse.function
+++ b/tests/suites/test_suite_x509parse.function
@@ -6,6 +6,7 @@
 #include "mbedtls/pem.h"
 #include "mbedtls/oid.h"
 #include "mbedtls/base64.h"
+#include "string.h"
 
 #if MBEDTLS_X509_MAX_INTERMEDIATE_CA > 19
 #error "The value of MBEDTLS_X509_MAX_INTERMEDIATE_C is larger \