diff --git a/.travis.yml b/.travis.yml
index 966f1b81..0cea1208 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,6 +2,7 @@ language: cpp
 
 os:
   - linux
+  - osx
 
 script:
   - export TOP=$(pwd)
diff --git a/test_common/harness/imageHelpers.cpp b/test_common/harness/imageHelpers.cpp
index 3b47e271..7606d1a3 100644
--- a/test_common/harness/imageHelpers.cpp
+++ b/test_common/harness/imageHelpers.cpp
@@ -790,7 +790,6 @@ float get_max_relative_error( cl_image_format *format, image_sampler_data *sampl
     {
         if( sampler->filter_mode != CL_FILTER_NEAREST )
         {
-            extern cl_device_type   gDeviceType;
             // The maximum
             if( gDeviceType == CL_DEVICE_TYPE_GPU )
                 maxError += MAKE_HEX_FLOAT(0x1.0p-4f, 0x1L, -4);              // Some GPUs ain't so accurate