diff --git a/build b/build
index 000a4c553..a29f08eed 100755
--- a/build
+++ b/build
@@ -28,6 +28,11 @@ fi
 
 if [ -z $SKIP_TESTS ]; then
 
+    phantomjs --version
+    if [ "$?" != "0" ]; then
+        echo "phantomjs is required to run rspec tests; please install it"
+    fi
+
 	echo "running rspec tests"
 	bundle exec rspec
 	if [ "$?" = "0" ]; then