diff --git a/.circleci/config.yml b/.circleci/config.yml
index 67ef717..68ef11d 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -112,7 +112,11 @@ jobs:
       - setup_remote_docker
       - run:
           name: build
-          command: docker build --network host --build-arg=EMSCRIPTEN_VERSION=${CIRCLE_TAG}-upstream --tag emscripten/emsdk:${CIRCLE_TAG} ./docker
+          # TESTING: using fixed EMSCRIPTEN_VERSION.  Will revert this as
+          # soon as we've published docker image autoamtically using a test
+          # tag.
+          #command: docker build --network host --build-arg EMSCRIPTEN_VERSION=${CIRCLE_TAG} --tag emscripten/emsdk:${CIRCLE_TAG} ./docker
+          command: docker build --network host --build-arg EMSCRIPTEN_VERSION=1.39.18 --tag emscripten/emsdk:1.39.18 ./docker
       - run:
           name: tag image
           command: docker tag emscripten/emsdk:${CIRCLE_TAG} emscripten/emsdk:latest
diff --git a/docker/Dockerfile b/docker/Dockerfile
index 57eb6c4..1c1241b 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -3,7 +3,7 @@ FROM debian:buster AS stage_build
 # ------------------------------------------------------------------------------
 
 # Supports only 1.38.40+, accepts also '-upstream' variants
-ARG EMSCRIPTEN_VERSION=1.39.18
+ARG EMSCRIPTEN_VERSION=1.39.17
 
 # ------------------------------------------------------------------------------