diff --git a/gridded_glm/libexec/_minute_gridder.py b/gridded_glm/libexec/_minute_gridder.py
index ff36565572c4280fe108e2b65b383056abe56bee..87bdf71f06145a801a0f1f2edec6fc2e7f9eda85 100644
--- a/gridded_glm/libexec/_minute_gridder.py
+++ b/gridded_glm/libexec/_minute_gridder.py
@@ -330,6 +330,9 @@ if __name__ == '__main__':
         if len(fileglob) != 3:
             log.error("There are not (yet) three GLM files from this minute. This may be expected. Exiting.")
             exit(0)
+        if sorted(fileglob)[-1] != args.filenames[0]:
+            log.error("This is not the last file from this minute. Exiting.")
+            exit(0)
         args.filenames = fileglob
 
     # check that all of our inputs exist