diff --git a/ext/src/swow_buffer.c b/ext/src/swow_buffer.c
index 7f857d04..ab855d0d 100644
--- a/ext/src/swow_buffer.c
+++ b/ext/src/swow_buffer.c
@@ -1026,9 +1026,11 @@ static char *swow_buffer_realloc_standard(char *old_value, size_t new_size)
         zend_string_forget_hash_val(new_string);
     } else {
         new_string = zend_string_alloc(new_size, false);
-        memcpy(ZSTR_VAL(new_string), ZSTR_VAL(old_string), new_length);
-        if (old_string != NULL && !ZSTR_IS_INTERNED(old_string)) {
-            GC_DELREF(old_string);
+        if (old_string != NULL) {
+            memcpy(ZSTR_VAL(new_string), ZSTR_VAL(old_string), new_length);
+            if (!ZSTR_IS_INTERNED(old_string)) {
+                GC_DELREF(old_string);
+            }
         }
     }
     ZSTR_VAL(new_string)[ZSTR_LEN(new_string) = new_length] = '\0';