diff --git a/tests/tests.pro b/tests/tests.pro
index 78b78c84526..a7c5bc6bd23 100644
--- a/tests/tests.pro
+++ b/tests/tests.pro
@@ -1,2 +1,4 @@
 TEMPLATE=subdirs
 SUBDIRS += auto manual tools
+isEmpty(LLVM_INSTALL_DIR):LLVM_INSTALL_DIR=$$(LLVM_INSTALL_DIR)
+exists($$LLVM_INSTALL_DIR):SUBDIRS += unit