diff --git a/hooks/prepare-commit-msg b/hooks/prepare-commit-msg
index 6ade9aab2d4..d5bf5171b59 100755
--- a/hooks/prepare-commit-msg
+++ b/hooks/prepare-commit-msg
@@ -2,7 +2,7 @@
 
 errors=0
 for file in $(git diff --cached --name-only | grep "\.go"); do
-  diff="$(gofmt -d "${file}")"
+  diff="$(git show ":${file}" | gofmt -d)"
   if [[ -n "$diff" ]]; then
     echo "# *** ERROR: *** File ${file} has not been gofmt'd." >> $1
     errors=1