diff --git a/.travis.yml b/.travis.yml
index 8683a39..ac76a5c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -16,7 +16,7 @@ before_install:
 script:
  - mkdir build
  - cd build
- - if [ -z ${QT4_BUILD+x} ]; then cmake -DBUILD_TESTS=TRUE -DQT4_BUILD=FALSE ..; else cmake -DBUILD_TESTS=TRUE -DQT4_BUILD=TRUE ..; fi
+ - if [ "$QT4_BUILD" == "OFF" ]; then cmake -DBUILD_TESTS=TRUE -DQT4_BUILD=FALSE ..; else cmake -DBUILD_TESTS=TRUE -DQT4_BUILD=TRUE ..; fi
  - make
  - export CTEST_OUTPUT_ON_FAILURE=1
  - make test