diff --git a/src/error.c b/src/error.c
index 14d0047d..70b62042 100644
--- a/src/error.c
+++ b/src/error.c
@@ -22,7 +22,7 @@ void jsonp_error_set_source(json_error_t *error, const char *source) {
 
     length = strlen(source);
     if (length < JSON_ERROR_SOURCE_LENGTH)
-        strncpy(error->source, source, length + 1);
+        strncpy(error->source, source, JSON_ERROR_SOURCE_LENGTH);
     else {
         size_t extra = length - JSON_ERROR_SOURCE_LENGTH + 4;
         memcpy(error->source, "...", 3);