mercurial/scmutil.py

--- a/mercurial/scmutil.py	Mon Nov 23 10:39:51 2020 -0800
+++ b/mercurial/scmutil.py	Fri Oct 16 19:03:09 2020 +0530
@@ -1580,6 +1580,9 @@
         writerequires(repo.vfs, wcreq)
     if storereq is not None:
         writerequires(repo.svfs, storereq)
+    elif repo.ui.configbool(b'format', b'usestore'):
+        # only remove store requires if we are using store
+        repo.svfs.tryunlink(b'requires')
 
 
 def writerequires(opener, requirements):