diff --git a/testing/coverage/coverall b/testing/coverage/coverall
index 00e1fd8c..36141432 100755
--- a/testing/coverage/coverall
+++ b/testing/coverage/coverall
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-if [ -z ${TRAVIS_TAG+x} ]; then
+if [ -z "${TRAVIS_TAG}" ]; then
   exit 0
 fi