diff --git a/fuzzing/CMakeLists.txt b/fuzzing/CMakeLists.txt
index 84278e8cdb3ab7ef117bc18cce07ccd87ca967d1..587368d066c539eaa527654499c2fab9bb98f008 100644
--- a/fuzzing/CMakeLists.txt
+++ b/fuzzing/CMakeLists.txt
@@ -28,6 +28,6 @@ if (ENABLE_FUZZING)
 endif()
 
 if(ENABLE_CJSON_TEST)
-    ADD_EXECUTABLE(fuzz_main fuzz_main.c)
+    ADD_EXECUTABLE(fuzz_main fuzz_main.c cjson_read_fuzzer.c)
     TARGET_LINK_LIBRARIES(fuzz_main cjson)
 endif()
\ No newline at end of file
diff --git a/fuzzing/cjson_read_fuzzer.cc b/fuzzing/cjson_read_fuzzer.c
similarity index 77%
rename from fuzzing/cjson_read_fuzzer.cc
rename to fuzzing/cjson_read_fuzzer.c
index 4ec432203d26274f58cc920bb6ac0dddbe270937..b2692eddb35416726fe6f8c44f7646783de2d8c1 100644
--- a/fuzzing/cjson_read_fuzzer.cc
+++ b/fuzzing/cjson_read_fuzzer.c
@@ -4,9 +4,8 @@
 
 #include "../cJSON.h"
 
-#ifdef __cplusplus
-extern "C"
-#endif
+int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size); /* required by C89 */
+
 int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
     cJSON *json;
@@ -17,6 +16,7 @@ int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 
 
     if(size <= offset) return 0;
+    if(data[size-1] != '\0') return 0;
     if(data[0] != '1' && data[0] != '0') return 0;
     if(data[1] != '1' && data[1] != '0') return 0;
     if(data[2] != '1' && data[2] != '0') return 0;
@@ -27,19 +27,9 @@ int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
     formatted           = data[2] == '1' ? 1 : 0;
     buffered            = data[3] == '1' ? 1 : 0;
 
-    copied = (unsigned char*)malloc(size);
-    if(copied == NULL) return 0;
-
-    memcpy(copied, data, size);
-    copied[size-1] = '\0';
-
-    json = cJSON_ParseWithOpts((const char*)copied + offset, NULL, require_termination);
+    json = cJSON_ParseWithOpts((const char*)data + offset, NULL, require_termination);
 
-    if(json == NULL)
-    {
-        free(copied);
-        return 0;
-    }
+    if(json == NULL) return 0;
 
     if(buffered)
     {
@@ -62,11 +52,17 @@ int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 
     if(minify)
     {
+        copied = (unsigned char*)malloc(size);
+        if(copied == NULL) return 0;
+
+        memcpy(copied, data, size);
+
         cJSON_Minify((char*)copied + offset);
+
+        free(copied);
     }
 
     cJSON_Delete(json);
-    free(copied);
 
     return 0;
 }
diff --git a/fuzzing/fuzz_main.c b/fuzzing/fuzz_main.c
index e004115fb9ad53b98116905e0039e5c12e458674..09dc15652af57c1dd2b0208192459d5b753e3a74 100644
--- a/fuzzing/fuzz_main.c
+++ b/fuzzing/fuzz_main.c
@@ -2,9 +2,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size); /* required by C90 */
-
-#include "cjson_read_fuzzer.cc"
+int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size); /* required by C89 */
 
 /* fuzz target entry point, works without libFuzzer */
 
diff --git a/fuzzing/ossfuzz.sh b/fuzzing/ossfuzz.sh
index 8de60e4aefe0add8da4a930229c1969131238ab6..fe4bf1601de1d35aec9a4fd08a896cd3e099a8fe 100644
--- a/fuzzing/ossfuzz.sh
+++ b/fuzzing/ossfuzz.sh
@@ -8,8 +8,8 @@ cd build
 cmake -DBUILD_SHARED_LIBS=OFF -DENABLE_CJSON_TEST=OFF ..
 make -j$(nproc)
 
-$CXX $CXXFLAGS -std=c++11 -I. \
-    $SRC/cjson/fuzzing/cjson_read_fuzzer.cc \
+$CC $CFLAGS -std=c89 -I. \
+    $SRC/cjson/fuzzing/cjson_read_fuzzer.c \
     -o $OUT/cjson_read_fuzzer \
     $LIB_FUZZING_ENGINE $SRC/cjson/build/libcjson.a