diff --git a/src/gnss.c b/src/gnss.c
index 741caa9..5b15b8d 100644
--- a/src/gnss.c
+++ b/src/gnss.c
@@ -271,13 +271,19 @@ static void init_assistance_data_upload_start(struct EG25Manager *manager,
                                               const char *response)
 {
     gchar value[BUFFER_SIZE];
-    long int size;
+    off_t size;
 
     /* Process AT response */
     at_process_result(manager, response);
 
     /* Get file size in bytes */
-    size = (long int)lseek(manager->gnss_assistance_fd, 0, SEEK_END);
+    size = lseek(manager->gnss_assistance_fd, 0, SEEK_END);
+    if (size == -1) {
+        g_critical("gnss: unable to read size of xtra data file: %s", g_strerror(errno));
+
+        manager->gnss_assistance_step = EG25_GNSS_STEP_LAST;
+        return;
+    }
     lseek(manager->gnss_assistance_fd, 0, SEEK_SET);
 
     /* Start upload */
@@ -308,7 +314,12 @@ static void upload_assistance_data(struct EG25Manager *manager)
     struct stat sb;
 
     if (fstat(manager->gnss_assistance_fd, &sb) != 0) {
-        g_error("Unable to upload xtra data: %s", g_strerror(errno));
+        g_critical("gnss: unable to stat xtra data file: %s", g_strerror(errno));
+
+        /* Make sure the upload times out and the modem goes back to AT command mode */
+        sleep(UPLOAD_TIMEOUT_S + 1);
+        manager->gnss_assistance_step = EG25_GNSS_STEP_LAST;
+        return;
     }
 
     do {