diff --git a/.ci/travis/linux/before_script.sh b/.ci/travis/linux/before_script.sh
index f5fa691ce21..e7e102d7b68 100755
--- a/.ci/travis/linux/before_script.sh
+++ b/.ci/travis/linux/before_script.sh
@@ -23,7 +23,7 @@ source $(git rev-parse --show-toplevel)/.ci/travis/scripts/travis_envvar_helper.
 DOCKER_DEPS_PUSH=$( [[ $TRAVIS_REPO_SLUG =~ qgis/QGIS ]] && [[ $TRAVIS_EVENT_TYPE =~ push ]] && echo "true" || echo "false" )
 DOCKER_DEPS_IMAGE_REBUILD=$( [[ $TRAVIS_COMMIT_MESSAGE =~ '[docker] update dependencies' ]] && echo "true" || echo "false" )
 # on cron job, QGIS image is built and push without testing
-DOCKER_QGIS_IMAGE_BUILD_PUSH=create_qgis_image
+DOCKER_QGIS_IMAGE_BUILD_PUSH=$(create_qgis_image)
 QGIS_LAST_BUILD_SUCCESS=true # TODO use API to know if last build succeed https://developer.travis-ci.com/resource/builds
 
 
@@ -43,7 +43,7 @@ echo "travis_fold:end:travis_env"
 echo "travis_fold:start:docker_build"
 echo "${bold}Docker build deps${endbold}"
 docker --version
-if [[ $DOCKER_QGIS_IMAGE_BUILD_PUSH -eq 0 ]]; then
+if [[ $DOCKER_QGIS_IMAGE_BUILD_PUSH =~ false ]]; then
   docker-compose --version
   docker-compose -f $DOCKER_COMPOSE config
 fi
diff --git a/.ci/travis/linux/script.sh b/.ci/travis/linux/script.sh
index 927362dc9fe..f9ce9cd8558 100755
--- a/.ci/travis/linux/script.sh
+++ b/.ci/travis/linux/script.sh
@@ -17,11 +17,11 @@ set -e
 
 source $(git rev-parse --show-toplevel)/.ci/travis/scripts/travis_envvar_helper.sh
 
-DOCKER_QGIS_IMAGE_BUILD_PUSH=create_qgis_image
+DOCKER_QGIS_IMAGE_BUILD_PUSH=$(create_qgis_image)
 
 mkdir -p $CCACHE_DIR
 
-if [[ $DOCKER_QGIS_IMAGE_BUILD_PUSH -eq 1 ]]; then
+if [[ $DOCKER_QGIS_IMAGE_BUILD_PUSH =~ true ]]; then
   DIR=$(git rev-parse --show-toplevel)/.docker
   pushd ${DIR}
   echo "${bold}Building QGIS Docker image '${DOCKER_TAG}'...${endbold}"
diff --git a/.ci/travis/scripts/travis_envvar_helper.sh b/.ci/travis/scripts/travis_envvar_helper.sh
index 5147ac7e7f5..68396d1caba 100644
--- a/.ci/travis/scripts/travis_envvar_helper.sh
+++ b/.ci/travis/scripts/travis_envvar_helper.sh
@@ -1,12 +1,14 @@
 #!/usr/bin/env bash
 
-function create_qgis_image {
+create_qgis_image () {
 
 if [[ ! $TRAVIS_REPO_SLUG =~ qgis/QGIS ]]; then
-  return 0
+  echo false
+  return
 fi
 if [[ $TRAVIS_EVENT_TYPE =~ cron ]] || [[ -n $TRAVIS_TAG ]]; then
-  return 1;
+  echo true
+  return
 fi
-return 0;
+echo false
 }