diff --git a/test_harness.jl b/test_harness.jl
index a80db03..1c2da18 100644
--- a/test_harness.jl
+++ b/test_harness.jl
@@ -25,8 +25,10 @@ if haskey(ENV, "GITHUB_SHA") && get(ENV, "GITHUB_EVENT_NAME", "") == "pull_reque
 
         # Check if there's any difference between the merge commit and the PR head
         # In GitHub Actions, HEAD^2 is the PR head (second parent of merge commit)
-        # success() returns true if the command exits with 0 (no differences)
-        has_diff = !success(`git diff --quiet --exit-code HEAD^2 HEAD`)
+        # Compare tree hashes to check if content actually differs
+        merge_tree = chomp(read(`git rev-parse HEAD^{tree}`, String))
+        pr_tree = chomp(read(`git rev-parse HEAD^2^{tree}`, String))
+        has_diff = merge_tree != pr_tree
 
         if has_diff
             base_branch = isempty(base_branch_name) ? "the base branch" : "'$base_branch_name'"