diff --git a/client/jansson/error.c b/client/jansson/error.c
index fd2557367..06dc837ec 100644
--- a/client/jansson/error.c
+++ b/client/jansson/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, JSON_ERROR_SOURCE_LENGTH);
+        strncpy(error->source, source, JSON_ERROR_SOURCE_LENGTH - 1);
     } else {
         size_t extra = length - JSON_ERROR_SOURCE_LENGTH + 4;
         memcpy(error->source, "...", 3);