diff --git a/ci/test/03_test_script.sh b/ci/test/03_test_script.sh
index 05e4d8fd54a..3e07f1c86d2 100755
--- a/ci/test/03_test_script.sh
+++ b/ci/test/03_test_script.sh
@@ -41,7 +41,10 @@ echo "=== BEGIN env ==="
 env
 echo "=== END env ==="
 
-(
+# Don't apply patches in the tidy job, because it relies on the `git diff`
+# command to detect IWYU errors. It is safe to skip this patch in the tidy job
+# because it doesn't run a UB detector.
+if [ "$RUN_TIDY" != "true" ]; then
   # compact->outputs[i].file_size is uninitialized memory, so reading it is UB.
   # The statistic bytes_written is only used for logging, which is disabled in
   # CI, so as a temporary minimal fix to work around UB and CI failures, leave
@@ -62,7 +65,7 @@ echo "=== END env ==="
    mutex_.Lock();
    stats_[compact->compaction->level() + 1].Add(stats);
 EOF
-)
+fi
 
 if [ "$RUN_FUZZ_TESTS" = "true" ]; then
   export DIR_FUZZ_IN=${DIR_QA_ASSETS}/fuzz_corpora/