diff --git a/polly/utils/check_format.sh b/polly/utils/check_format.sh
index 36b24b4f9102..671d15e0045b 100755
--- a/polly/utils/check_format.sh
+++ b/polly/utils/check_format.sh
@@ -1,5 +1,10 @@
 #!/bin/bash
 
+if ! which clang-format; then
+    echo "Error: cannot find clang-format in your path"
+    exit 1
+fi
+
 OK=0
 
 for ARG in "$@"
@@ -13,7 +18,9 @@ for ARG in "$@"
 
 if [[ $OK -eq "1" ]]; then
   echo "Error: clang-format reported formatting differences"
+  exit 1
 else
   echo "OK: clang-format reported no formatting differences"
+  exit 0
 fi