diff --git a/src/test_lib_json/fuzz.h b/src/test_lib_json/fuzz.h
index d5bc08e..0816d27 100644
--- a/src/test_lib_json/fuzz.h
+++ b/src/test_lib_json/fuzz.h
@@ -9,6 +9,6 @@
 #include <cstddef>
 #include <stdint.h>
 
-int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size);
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size);
 
 #endif // ifndef FUZZ_H_INCLUDED