diff --git a/src/value.c b/src/value.c
index 1b69904..417ea85 100644
--- a/src/value.c
+++ b/src/value.c
@@ -723,6 +723,7 @@ int json_string_setn_nocheck(json_t *json, const char *value, size_t len)
     string = json_to_string(json);
     jsonp_free(string->value);
     string->value = dup;
+    string->length = len;
 
     return 0;
 }