diff --git a/reformat.sh b/reformat.sh
index ba66febaa..b58ea8323 100755
--- a/reformat.sh
+++ b/reformat.sh
@@ -1,5 +1,6 @@
 # reformat the code
-find . -name "*.cpp" -or -name "*.h" -exec clang-format -i {} \;
+# no operator is implicit -a with higher precedence than -o
+find . \( -name "*.cpp" -or -name "*.h" \) -exec clang-format -i {} \;
 
 # check in the result
 git commit -a -m "GIT_SILENT: application of coding style"