diff --git a/test/sharness/t0300-docker-image.sh b/test/sharness/t0300-docker-image.sh
index 478b24344..ec964cd0d 100755
--- a/test/sharness/t0300-docker-image.sh
+++ b/test/sharness/t0300-docker-image.sh
@@ -33,7 +33,10 @@ TEST_TESTS_DIR=$(dirname "$TEST_SCRIPTS_DIR")
 APP_ROOT_DIR=$(dirname "$TEST_TESTS_DIR")
 
 test_expect_success "docker image build succeeds" '
-	docker_build "$TEST_TESTS_DIR/Dockerfile" "$APP_ROOT_DIR" >actual
+	docker_build "$TEST_TESTS_DIR/Dockerfile" "$APP_ROOT_DIR" >actual ||
+	test_fsh echo "TEST_TESTS_DIR: $TEST_TESTS_DIR" ||
+	test_fsh echo "APP_ROOT_DIR : $APP_ROOT_DIR" ||
+	test_fsh cat actual
 '
 
 test_expect_success "docker image build output looks good" '