diff --git a/library/error.c b/library/error.c
index b5bd8d7..afad389 100644
--- a/library/error.c
+++ b/library/error.c
@@ -893,8 +893,6 @@
     return( NULL );
 }
 
-void (*mbedtls_test_hook_error_add)( int, int, const char *, int );
-
 void mbedtls_strerror( int ret, char *buf, size_t buflen )
 {
     size_t len;
@@ -975,4 +973,8 @@
 
 #endif /* MBEDTLS_ERROR_C */
 
+#if defined(MBEDTLS_TEST_HOOKS)
+void (*mbedtls_test_hook_error_add)( int, int, const char *, int );
+#endif
+
 #endif /* MBEDTLS_ERROR_C || MBEDTLS_ERROR_STRERROR_DUMMY */