diff --git a/src/gnss.c b/src/gnss.c
index 502612c..6503943 100644
--- a/src/gnss.c
+++ b/src/gnss.c
@@ -216,7 +216,8 @@ static void fetch_assistance_data(struct EG25Manager *manager)
     }
 
     lseek(manager->gnss_assistance_fd, 0, SEEK_SET);
-    ftruncate(manager->gnss_assistance_fd, 0);
+    if (ftruncate(manager->gnss_assistance_fd, 0) < 0)
+        g_warning("Unable to truncate file, assistance data might be invalid!");
     url = g_strconcat(manager->gnss_assistance_url, "/",
                       manager->gnss_assistance_file, NULL);