diff --git a/docker/develop/questing-slim/Dockerfile b/docker/develop/questing-slim/Dockerfile
index 4ed9b5911..be78570da 100644
--- a/docker/develop/questing-slim/Dockerfile
+++ b/docker/develop/questing-slim/Dockerfile
@@ -32,7 +32,7 @@ ENV PHOTOPRISM_ARCH=$TARGETARCH \
     TF_CPP_MIN_LOG_LEVEL=4 \
     TF_ENABLE_ONEDNN_OPTS=1 \
     MALLOC_ARENA_MAX=2 \
-    PROG="photoprism"
+    PROG="photoprism" \
     S6_KEEP_ENV=0 \
     S6_VERBOSITY=0 \
     S6_LOGGING=0
diff --git a/docker/develop/questing/Dockerfile b/docker/develop/questing/Dockerfile
index bb3b0d5b6..d8f47d964 100644
--- a/docker/develop/questing/Dockerfile
+++ b/docker/develop/questing/Dockerfile
@@ -37,7 +37,7 @@ ENV PHOTOPRISM_ARCH=$TARGETARCH \
     GOBIN="/usr/local/bin" \
     GO111MODULE="on" \
     CGO_CFLAGS="-g -O2 -Wno-return-local-addr" \
-    PROG="photoprism"
+    PROG="photoprism" \
     S6_KEEP_ENV=1 \
     S6_VERBOSITY=0 \
     S6_LOGGING=0