diff --git a/mercurial/store.py b/mercurial/store.py
--- a/mercurial/store.py
+++ b/mercurial/store.py
@@ -481,6 +481,8 @@
                 # chunksize, so let's keep iterating
                 pass
 
+        if chunk:
+            raise error.Abort(_("fncache does not ends with a newline"))
         self._checkentries(fp)
         fp.close()