diff --git a/py/mpconfig.h b/py/mpconfig.h
index 4a3288a3d..0aefd1b35 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -381,3 +381,8 @@ typedef double mp_float_t;
 #ifndef NORETURN
 #define NORETURN __attribute__((noreturn))
 #endif
+
+// Modifier for weak functions
+#ifndef MP_WEAK
+#define MP_WEAK __attribute__((weak))
+#endif
diff --git a/stmhal/main.c b/stmhal/main.c
index e264fdf4b..b74fa7318 100644
--- a/stmhal/main.c
+++ b/stmhal/main.c
@@ -111,11 +111,11 @@ void nlr_jump_fail(void *val) {
 }
 
 #ifndef NDEBUG
-void __attribute__((weak))
-    __assert_func(const char *file, int line, const char *func, const char *expr) {
+void MP_WEAK __assert_func(const char *file, int line, const char *func, const char *expr) {
     (void)func;
     printf("Assertion '%s' failed, at file %s:%d\n", expr, file, line);
     __fatal_error("");
+    while (1);
 }
 #endif