diff --git a/src/test_lib_json/fuzz.h b/src/test_lib_json/fuzz.h
index f650437..60897a4 100644
--- a/src/test_lib_json/fuzz.h
+++ b/src/test_lib_json/fuzz.h
@@ -6,9 +6,9 @@
 #ifndef FUZZ_H_INCLUDED
 #define FUZZ_H_INCLUDED
 
-#include <stddef.h>
-#include <stdint.h>
+#include <cstddef>
+#include <cstdint>
 
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size);
+int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size);
 
 #endif // ifndef FUZZ_H_INCLUDED