diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -588,8 +588,14 @@ def diffordiffstat(ui, repo, diffopts, n
         ctx1 = repo[node1]
         ctx2 = repo[node2]
         for subpath, sub in subrepo.itersubrepos(ctx1, ctx2):
-            if node2 is not None:
-                node2 = ctx2.substate[subpath][1]
+            try:
+                if node2 is not None:
+                    node2 = ctx2.substate[subpath][1]
+            except KeyError:
+                # A subrepo that existed in node1 was deleted between node1 and
+                # node2 (inclusive). Thus, ctx2's substate won't contain that
+                # subpath. The best we can do is to ignore it.
+                node2 = None
             submatch = matchmod.narrowmatcher(subpath, match)
             sub.diff(diffopts, node2, submatch, changes=changes,
                      stat=stat, fp=fp, prefix=prefix)