diff --git a/Makefile b/Makefile
index fae3cac81a4717d2a6b96b475a59f31546a16015..0f2e27cdec6fb3861b7348e2d93eddc31ae688c2 100644
--- a/Makefile
+++ b/Makefile
@@ -64,7 +64,7 @@ install-python-requirements:
 	@echo "+-----------------------------+"
 	@echo "| installing Python modules   |"
 	@echo "+-----------------------------+"
-	    pip install --user -U -r $(CURDIR)/requirements.txt
+		if [ -z $VIRTUAL_ENV ]; then pip install --user -U -r $(CURDIR)/requirements.txt; else pip install -U -r $(CURDIR)/requirements.txt; fi
 	@echo "+-----------------------------+"
 	@echo "| installed Python modules    |"
 	@echo "+-----------------------------+"