diff --git a/.travis.yml b/.travis.yml
index 3f26b319a8188d21135d4ec64787abb6fa8d29ec..04db99a47b9d332ba7badfa4a728b2edb25182e4 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -46,7 +46,7 @@ sudo: false
 addons:
   apt:
     packages:
-      - python
+      - gfortran
       - graphviz
       - libyaml-dev
 
@@ -79,7 +79,7 @@ before_script:
 script: share/spack/qa/run-$TEST_SUITE-tests
 
 after_success:
-  - if [[ $TEST_SUITE == unit && $TRAVIS_PYTHON_VERSION == 2.7 ]]; then coveralls; fi
+  - if [[ $TEST_SUITE == unit && $TRAVIS_PYTHON_VERSION == 2.7 && $TRAVIS_OS_NAME == "linux" ]]; then coveralls; fi
 
 #=============================================================================
 # Notifications
diff --git a/share/spack/qa/run-unit-tests b/share/spack/qa/run-unit-tests
index 0728614bc8495b3d6d0aab9ab89cbfe37f1193b3..9cace0dfd66b6ee6e5f0c187d69c4e62a50cffb1 100755
--- a/share/spack/qa/run-unit-tests
+++ b/share/spack/qa/run-unit-tests
@@ -40,12 +40,13 @@ cd "$SPACK_ROOT"
 source "$SPACK_ROOT/share/spack/setup-env.sh"
 spack compilers
 spack config get compilers
-spack install -v libdwarf
 
 # Run unit tests with code coverage
 if [[ "$TRAVIS_PYTHON_VERSION" == 2.7 ]]; then
+    coverage run bin/spack install -v libdwarf
     coverage run bin/spack test "$@"
     coverage combine
 else
+    spack install -v libdwarf
     spack test "$@"
 fi