diff --git a/.travis.yml b/.travis.yml
index c157f7c87..94e13bfeb 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -439,8 +439,8 @@ matrix:
                       - zlib1g-dev
 
 before_install:
-    - export "${OVERRIDE_CC}"
-    - export "${OVERRIDE_CXX}"
+  - export "${OVERRIDE_CC-blank=}"
+  - export "${OVERRIDE_CXX-blank=}"
 
 install:
   - if [ "$T" = "coverage" ]; then pip2 install --user cpp-coveralls; fi