diff --git a/sapi/fuzzer/fuzzer-execute-common.h b/sapi/fuzzer/fuzzer-execute-common.h
index f5113a5b0e41f..081ab4d30e823 100644
--- a/sapi/fuzzer/fuzzer-execute-common.h
+++ b/sapi/fuzzer/fuzzer-execute-common.h
@@ -127,15 +127,16 @@ ZEND_ATTRIBUTE_UNUSED static void create_file(void) {
 ZEND_ATTRIBUTE_UNUSED static void opcache_invalidate(void) {
 	steps_left = MAX_STEPS;
 	zend_exception_save();
-	zval retval, func, args[2];
-	ZVAL_STRING(&func, "opcache_invalidate");
+	zval retval, args[2];
+	zend_function *fn = zend_hash_str_find_ptr(CG(function_table), ZEND_STRL("opcache_invalidate"));
+	ZEND_ASSERT(fn != NULL);
+
 	ZVAL_STRING(&args[0], FILE_NAME);
 	ZVAL_TRUE(&args[1]);
-	call_user_function(CG(function_table), NULL, &func, &retval, 2, args);
+	zend_call_known_function(fn, NULL, NULL, &retval, 2, args, NULL);
 	ZEND_ASSERT(Z_TYPE(retval) == IS_TRUE);
 	zval_ptr_dtor(&args[0]);
 	zval_ptr_dtor(&retval);
-	zval_ptr_dtor(&func);
 	zend_exception_restore();
 }
 
diff --git a/sapi/fuzzer/fuzzer-sapi.c b/sapi/fuzzer/fuzzer-sapi.c
index baf77ae0463b3..5014a51cca4f2 100644
--- a/sapi/fuzzer/fuzzer-sapi.c
+++ b/sapi/fuzzer/fuzzer-sapi.c
@@ -292,11 +292,13 @@ int fuzzer_do_request_from_buffer(
 
 // Call named PHP function with N zval arguments
 void fuzzer_call_php_func_zval(const char *func_name, int nargs, zval *args) {
-	zval retval, func;
+	zval retval;
+
+	zend_function *fn = zend_hash_str_find_ptr(CG(function_table), func_name, strlen(func_name));
+	ZEND_ASSERT(fn != NULL);
 
-	ZVAL_STRING(&func, func_name);
 	ZVAL_UNDEF(&retval);
-	call_user_function(CG(function_table), NULL, &func, &retval, nargs, args);
+	zend_call_known_function(fn, NULL, NULL, &retval, nargs, args, NULL);
 
 	// TODO: check result?
 	/* to ensure retval is not broken */
@@ -304,7 +306,6 @@ void fuzzer_call_php_func_zval(const char *func_name, int nargs, zval *args) {
 
 	/* cleanup */
 	zval_ptr_dtor(&retval);
-	zval_ptr_dtor(&func);
 }
 
 // Call named PHP function with N string arguments