diff --git a/src/checker.cpp b/src/checker.cpp
index dd61f6fc3..48863e706 100644
--- a/src/checker.cpp
+++ b/src/checker.cpp
@@ -6894,7 +6894,10 @@ gb_internal void check_deferred_procedures(Checker *c) {
 			continue;
 		}
 
-		GB_ASSERT(is_type_proc(src->type));
+		if (!is_type_proc(src->type)) {
+			error(src->token, "Invalid procedure type found during deferred procedure checking");
+			continue;
+		}
 		GB_ASSERT(is_type_proc(dst->type));
 		Type *src_params = base_type(src->type)->Proc.params;
 		Type *src_results = base_type(src->type)->Proc.results;