Set the option on the cmake line
diff --git a/.travis.yml b/.travis.yml
index 1477fca..5b367e0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,13 +9,13 @@
 env:
   - USE_CONTEXT=ON
   - USE_CONTEXT=OFF
-  - USE_CONTEXT=OFF use_embedtls=ON
+  - USE_CONTEXT=OFF USE_EMBEDTLS=ON
 matrix:
   exclude:
     - compiler: gcc
       env: USE_CONTEXT=OFF
     - compiler: gcc
-      env: USE_CONTEXT=OFF use_embedtls=ON
+      env: USE_CONTEXT=OFF USE_EMBEDTLS=ON
 addons:
   apt:
     sources:
@@ -27,7 +27,7 @@
 script:
   - git clone git://github.com/cose-wg/Examples Examples
   - mkdir build
-  - cd build && cmake -Duse_context=$USE_CONTEXT -Dcoveralls_send=ON .. && make all test
+  - cd build && cmake -Duse_context=$USE_CONTEXT -Dcoveralls_send=ON -Duse_embedtls=$USE_EMBEDTLS .. && make all test
   - make coveralls