diff --git a/diff-sha.sh b/diff-sha.sh
index 988c598a..434f2899 100644
--- a/diff-sha.sh
+++ b/diff-sha.sh
@@ -66,9 +66,6 @@ if [[ -z $GITHUB_BASE_REF ]]; then
     if [[ -z "$PREVIOUS_SHA" || "$PREVIOUS_SHA" == "0000000000000000000000000000000000000000" ]]; then
       PREVIOUS_SHA=$(git rev-parse "$(git branch -r --sort=-committerdate | head -1)")
     fi
-    if [[ "$INPUT_SHA" == "$PREVIOUS_SHA" ]]; then
-      PREVIOUS_SHA=$(git rev-parse "$INPUT_SHA^1")
-    fi
 
     if [[ "$PREVIOUS_SHA" == "$CURRENT_SHA" ]]; then
       INITIAL_COMMIT="true"