diff --git a/hgext3rd/fbsparse.py b/hgext3rd/fbsparse.py
--- a/hgext3rd/fbsparse.py
+++ b/hgext3rd/fbsparse.py
@@ -348,17 +348,20 @@
     entry = commands.table['^diff']
     entry[1].append(('s', 'sparse', None,
                      'only show changes in files in the sparse config'))
-    # wrap workingfilectx's data function to return the data for files
-    # outside the sparse checkout by fetching from the working copy parent.
+
     def workingfilectxdata(orig, self):
-        if not util.safehasattr(self.repo(), 'sparsematch'):
+        try:
+            # Try lookup working copy first.
             return orig(self)
-        sparsematch = self.repo().sparsematch()
-        if sparsematch(self._path):
-            return orig(self)
-        else:
-            basectx = self._changectx._parents[0]
-            return basectx[self._path].data()
+        except IOError:
+            # Then try working copy parent if the file is outside sparse.
+            if util.safehasattr(self._repo, 'sparsematch'):
+                sparsematch = self._repo.sparsematch()
+                if not sparsematch(self._path):
+                    basectx = self._changectx._parents[0]
+                    return basectx[self._path].data()
+            raise
+
     extensions.wrapfunction(context.workingfilectx, 'data', workingfilectxdata)
 
     # wrap trydiff to filter diffs if '--sparse' is set
diff --git a/tests/test-sparse-rebase.t b/tests/test-sparse-rebase.t
--- a/tests/test-sparse-rebase.t
+++ b/tests/test-sparse-rebase.t
@@ -24,5 +24,6 @@
   temporarily included 1 file(s) in the sparse checkout for merging
   cleaned up 1 temporarily added file(s) from the sparse checkout
   rebasing 3:e7b3f00ed42e "D" (D tip)
-  abort: D@bbfdd6cb49aa: not found in manifest!
-  [255]
+  temporarily included 1 file(s) in the sparse checkout for merging
+  cleaned up 1 temporarily added file(s) from the sparse checkout
+  saved backup bundle to $TESTTMP/repo/.hg/strip-backup/dc0947a82db8-b8481714-rebase.hg (glob)