diff --git a/action.yml b/action.yml
index 483c70fc..0e21d02f 100644
--- a/action.yml
+++ b/action.yml
@@ -83,12 +83,11 @@ inputs:
   fetch_depth:
     description: "Initial depth of the branch history fetched. **NOTE**: This can be adjusted to resolve errors with insufficient history."
     required: false
-    default: "40"
+    default: "50"
   max_fetch_depth:
     description: "Maximum depth of the branch history fetched. **NOTE**: This can be adjusted to resolve errors with insufficient history."
     required: false
-    default: "5000"
-    deprecationMessage: "This input is deprecated and will be removed in a future release."
+    default: "6000"
   since_last_remote_commit:
     description: "Use the last commit on the remote branch as the `base_sha`. Defaults to the last non merge commit on the target branch for pull request events and the previous remote commit of the current branch for push events."
     required: true
diff --git a/diff-sha.sh b/diff-sha.sh
index cb17a364..752705a2 100644
--- a/diff-sha.sh
+++ b/diff-sha.sh
@@ -239,6 +239,32 @@ else
   else
     PREVIOUS_SHA=$INPUT_BASE_SHA && exit_status=$? || exit_status=$?
   fi
+  
+  if [[ "$INPUT_SINCE_LAST_REMOTE_COMMIT" == "false" ]]; then
+    if [[ -f .git/shallow ]]; then
+      depth=$INPUT_FETCH_DEPTH
+      max_depth=$INPUT_MAX_FETCH_DEPTH
+
+      for ((i=0; i<max_depth; i+=depth)); do
+        if git diff --name-only --ignore-submodules=all "$PREVIOUS_SHA$DIFF$CURRENT_SHA" 1>/dev/null 2>&1; then
+          break
+        fi
+        
+        echo "Fetching $i commits..."
+
+        # shellcheck disable=SC2086
+        git fetch $EXTRA_ARGS -u --progress --deepen="$i" origin $TARGET_BRANCH $CURRENT_SHA 1>/dev/null 2>&1
+      done
+
+      if ((i > max_depth)); then
+        echo "::error::Unable to locate a common ancestor between $TARGET_BRANCH and $CURRENT_BRANCH with: $PREVIOUS_SHA$DIFF$CURRENT_SHA"
+        exit 1
+      fi
+    else
+      echo "::debug::Not a shallow clone, skipping merge-base check."
+    fi
+  fi
+  
 
   echo "::debug::Target branch: $TARGET_BRANCH"
   echo "::debug::Current branch: $CURRENT_BRANCH"