diff --git a/include/mbedtls/threading.h b/include/mbedtls/threading.h
index b0c34ec..d2d79a1 100644
--- a/include/mbedtls/threading.h
+++ b/include/mbedtls/threading.h
@@ -97,6 +97,9 @@
  */
 extern mbedtls_threading_mutex_t mbedtls_threading_readdir_mutex;
 extern mbedtls_threading_mutex_t mbedtls_threading_gmtime_mutex;
+#if defined(MBEDTLS_ECP_FUNCTION_ALT)
+extern mbedtls_threading_mutex_t mbedtls_threading_cryptohw_asym_mutex;
+#endif
 #endif /* MBEDTLS_THREADING_C */
 
 #ifdef __cplusplus