diff --git a/tests/unit/unittest/highlightingmarks-test.cpp b/tests/unit/unittest/highlightingmarks-test.cpp
index 577fa66fdd5..1d3ba1a05ec 100644
--- a/tests/unit/unittest/highlightingmarks-test.cpp
+++ b/tests/unit/unittest/highlightingmarks-test.cpp
@@ -107,7 +107,7 @@ struct Data {
     Utf8String filePath{Utf8StringLiteral(TESTDATA_DIR"/highlightingmarks.cpp")};
     Document document{filePath,
                       ProjectPart(Utf8StringLiteral("projectPartId"),
-                                  {Utf8StringLiteral("-std=c++14")}),
+                                  {Utf8StringLiteral("-std=c++14"), Utf8StringLiteral("-I" TESTDATA_DIR)}),
                       {},
                       documents};
     TranslationUnit translationUnit{filePath,