diff --git a/.travis.yml b/.travis.yml
index 7742248..5f3029f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,7 +8,8 @@ script:
 - make dist-src
 - make clean; SYSTEM=linux        make 
 - make clean; SYSTEM=linux-osmesa make
-- pushd build/cmake; cmake -G 'Unix Makefiles' .; make; popd
+- pushd build/cmake; git clean -xdf .; cmake -G 'Unix Makefiles' .                ; make; popd
+- pushd build/cmake; git clean -xdf .; cmake -G 'Unix Makefiles' -DGLEW_OSMESA=1 .; make; popd
 addons:
   artifacts:
     bucket: glew