diff --git a/tests/fuzz/CMakeLists.txt b/tests/fuzz/CMakeLists.txt
index 8ca2b8d5a..240002726 100644
--- a/tests/fuzz/CMakeLists.txt
+++ b/tests/fuzz/CMakeLists.txt
@@ -19,6 +19,8 @@
 # along with WeeChat.  If not, see <https://www.gnu.org/licenses/>.
 #
 
+enable_language(CXX)
+
 if(NOT DEFINED ENV{LIB_FUZZING_ENGINE})
   set(ENV{LIB_FUZZING_ENGINE} "-fsanitize=address,fuzzer")
 endif()
@@ -94,7 +96,7 @@ list(APPEND FUZZ_TARGET_DEPS
 set(FUZZ_CORE_TARGETS calc crypto string utf8)
 
 foreach(fuzz_target ${FUZZ_CORE_TARGETS})
-  add_executable(weechat_core_${fuzz_target}_fuzzer core/${fuzz_target}-fuzzer.c)
+  add_executable(weechat_core_${fuzz_target}_fuzzer core/${fuzz_target}-fuzzer.cc)
   target_link_libraries(weechat_core_${fuzz_target}_fuzzer ${FUZZ_TARGET_LINK} coverage_config)
   set_target_properties(weechat_core_${fuzz_target}_fuzzer PROPERTIES LINK_FLAGS "$ENV{LIB_FUZZING_ENGINE}")
   add_dependencies(weechat_core_${fuzz_target}_fuzzer ${FUZZ_TARGET_DEPS})
diff --git a/tests/fuzz/core/calc-fuzzer.c b/tests/fuzz/core/calc-fuzzer.cc
similarity index 93%
rename from tests/fuzz/core/calc-fuzzer.c
rename to tests/fuzz/core/calc-fuzzer.cc
index b7e0619a8..85719cefb 100644
--- a/tests/fuzz/core/calc-fuzzer.c
+++ b/tests/fuzz/core/calc-fuzzer.cc
@@ -21,15 +21,17 @@
 
 /* Fuzz testing on WeeChat core calc functions */
 
+extern "C"
+{
 #include <stdlib.h>
 #include <stdint.h>
 #include <stddef.h>
 #include <string.h>
 
 #include "src/core/core-calc.h"
+}
 
-int
-LLVMFuzzerTestOneInput (const uint8_t *data, size_t size)
+extern "C" int LLVMFuzzerTestOneInput (const uint8_t *data, size_t size)
 {
     char *str;
 
diff --git a/tests/fuzz/core/crypto-fuzzer.c b/tests/fuzz/core/crypto-fuzzer.cc
similarity index 98%
rename from tests/fuzz/core/crypto-fuzzer.c
rename to tests/fuzz/core/crypto-fuzzer.cc
index 00c5aead5..a8394412d 100644
--- a/tests/fuzz/core/crypto-fuzzer.c
+++ b/tests/fuzz/core/crypto-fuzzer.cc
@@ -21,6 +21,8 @@
 
 /* Fuzz testing on WeeChat core crypto functions */
 
+extern "C"
+{
 #include <stdlib.h>
 #include <stdint.h>
 #include <stddef.h>
@@ -33,8 +35,9 @@
 
 extern char *weecrypto_hash_algo_string[];
 extern int weecrypto_hash_algo[];
+}
 
-int
+extern "C" int
 LLVMFuzzerTestOneInput (const uint8_t *data, size_t size)
 {
     char *str, hash[1024], *result;
diff --git a/tests/fuzz/core/string-fuzzer.c b/tests/fuzz/core/string-fuzzer.cc
similarity index 97%
rename from tests/fuzz/core/string-fuzzer.c
rename to tests/fuzz/core/string-fuzzer.cc
index 86fe59722..e3d0cd1f5 100644
--- a/tests/fuzz/core/string-fuzzer.c
+++ b/tests/fuzz/core/string-fuzzer.cc
@@ -21,6 +21,8 @@
 
 /* Fuzz testing on WeeChat core string functions */
 
+extern "C"
+{
 #include <stdlib.h>
 #include <stdint.h>
 #include <stddef.h>
@@ -31,10 +33,11 @@
 #include "src/core/core-config.h"
 #include "src/core/core-string.h"
 #include "src/plugins/weechat-plugin.h"
+}
 
 regex_t global_regex;
 
-int
+extern "C" int
 LLVMFuzzerInitialize(int *argc, char ***argv)
 {
     (void) argc;
@@ -56,10 +59,11 @@ callback_replace (void *data, const char *text)
     return strdup ("z");
 }
 
-int
+extern "C" int
 LLVMFuzzerTestOneInput (const uint8_t *data, size_t size)
 {
-    char *str, *str2, **str_dyn, *result, *masks[3] = { "a*", "b*", NULL};
+    const char *masks[3] = { "a*", "b*", NULL};
+    char *str, *str2, **str_dyn, *result;
     char **argv, *buffer;
     const char *name;
     int argc, flags, num_tags, priority;
@@ -186,7 +190,7 @@ LLVMFuzzerTestOneInput (const uint8_t *data, size_t size)
 
     string_parse_size (str);
 
-    buffer = malloc ((size * 4) + 8 + 1);
+    buffer = (char *)malloc ((size * 4) + 8 + 1);
     string_base16_encode (str, size, buffer);
     string_base16_decode (str, buffer);
     string_base32_encode (str, size, buffer);
diff --git a/tests/fuzz/core/utf8-fuzzer.c b/tests/fuzz/core/utf8-fuzzer.cc
similarity index 98%
rename from tests/fuzz/core/utf8-fuzzer.c
rename to tests/fuzz/core/utf8-fuzzer.cc
index 9d8bac23e..11506133e 100644
--- a/tests/fuzz/core/utf8-fuzzer.c
+++ b/tests/fuzz/core/utf8-fuzzer.cc
@@ -21,6 +21,8 @@
 
 /* Fuzz testing on WeeChat core UTF-8 functions */
 
+extern "C"
+{
 #include <stdlib.h>
 #include <stdint.h>
 #include <stddef.h>
@@ -28,8 +30,9 @@
 
 #include "src/core/core-config.h"
 #include "src/core/core-utf8.h"
+}
 
-int
+extern "C" int
 LLVMFuzzerInitialize(int *argc, char ***argv)
 {
     (void) argc;
@@ -40,7 +43,7 @@ LLVMFuzzerInitialize(int *argc, char ***argv)
     return 0;
 }
 
-int
+extern "C" int
 LLVMFuzzerTestOneInput (const uint8_t *data, size_t size)
 {
     char *str, *str2, utf8_char[5], *error;