diff --git a/validation/Dockerfile b/validation/Dockerfile
index fb265fe3f0d4b865bdd899004ff4c2570a3762d1..725afb403e461fbfb5ef47e19bfdc66c0acc74cb 100644
--- a/validation/Dockerfile
+++ b/validation/Dockerfile
@@ -134,7 +134,7 @@ RUN set -e pipefail; \
 # switch to development version via build-arg
 ARG ADD_DEV
 RUN set -e pipefail; \
-    if test xYES == x`echo ${ADD_DEV} | tr '[:lower:]' '[:upper:]'`; then \
+    if test xYES = x`echo ${ADD_DEV} | tr '[:lower:]' '[:upper:]'`; then \
       apk add bash emacs gcc build-base; \
       /usr/local/bin/python -m pip install pylint black; \
       apk del gcc build-base; \