diff --git a/tests/common.h b/tests/common.h
index d5c8def..5317345 100644
--- a/tests/common.h
+++ b/tests/common.h
@@ -27,7 +27,6 @@
 
 extern void reset(cJSON *item);
 extern char *read_file(const char *filename);
-extern cjbool assert_is_invalid(cJSON *item);
 
 /* assertion helper macros */
 #define assert_has_type(item, item_type) TEST_ASSERT_BITS_MESSAGE(0xFF, item_type, item->type, "Item doesn't have expected type.")