diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -124,7 +124,7 @@
 
 format-c:
 	clang-format --style file -i \
-	  `hg files 'set:(**.c or **.h) and not "listfile:contrib/clang-format-blacklist"'`
+	  `hg files 'set:(**.c or **.cc or **.h) and not "listfile:contrib/clang-format-blacklist"'`
 
 update-pot: i18n/hg.pot
 
diff --git a/tests/test-check-clang-format.t b/tests/test-check-clang-format.t
--- a/tests/test-check-clang-format.t
+++ b/tests/test-check-clang-format.t
@@ -3,7 +3,7 @@
   $ . "$TESTDIR/helpers-testrepo.sh"
 
   $ cd "$TESTDIR"/..
-  $ for f in `testrepohg files 'set:(**.c or **.h) and not "listfile:contrib/clang-format-blacklist"'` ; do
+  $ for f in `testrepohg files 'set:(**.c or **.cc or **.h) and not "listfile:contrib/clang-format-blacklist"'` ; do
   >   clang-format --style file $f > $f.formatted
   >   cmp $f $f.formatted || diff -u $f $f.formatted
   >   rm $f.formatted