diff --git a/tools/fast8.sh b/tools/fast8.sh
index c1792ae68be..2b3e22abda5 100755
--- a/tools/fast8.sh
+++ b/tools/fast8.sh
@@ -1,13 +1,13 @@
 #!/bin/bash
 
 cd $(dirname "$0")/..
-CHANGED=$(git diff --name-only HEAD~2 | tr '\n' ' ')
+CHANGED=$(git diff --name-only HEAD~1 | tr '\n' ' ')
 
 # Skip files that don't exist
 # (have been git rm'd)
 CHECK=""
 for FILE in $CHANGED; do
-    if [ -f "$f" ]; then
+    if [ -f "$FILE" ]; then
         CHECK="$CHECK $FILE"
     fi
 done