diff --git a/.github/workflows/preview_build.yml b/.github/workflows/preview_build.yml
index 345a2152db..2a280a6fcd 100644
--- a/.github/workflows/preview_build.yml
+++ b/.github/workflows/preview_build.yml
@@ -76,7 +76,7 @@ jobs:
         echo "::group::CMake"
         emcmake cmake .. \
           -DHOST_BINARY_DIR=../build-host \
-          -DCMAKE_BUILD_TYPE=RelWithDebInfo \
+          -DCMAKE_BUILD_TYPE=Release \
           # EOF
         echo "::endgroup::"
 
diff --git a/os/emscripten/Dockerfile b/os/emscripten/Dockerfile
index cbbff38c15..5d54b54114 100644
--- a/os/emscripten/Dockerfile
+++ b/os/emscripten/Dockerfile
@@ -1,4 +1,4 @@
-FROM emscripten/emsdk:2.0.31
+FROM emscripten/emsdk:2.0.34
 
 COPY emsdk-liblzma.patch /
 RUN cd /emsdk/upstream/emscripten && patch -p1 < /emsdk-liblzma.patch
diff --git a/os/emscripten/README.md b/os/emscripten/README.md
index 59f17c6269..c78dc6727b 100644
--- a/os/emscripten/README.md
+++ b/os/emscripten/README.md
@@ -24,7 +24,7 @@ Next, build the game with emscripten:
 
 ```
   mkdir build
-  docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build emsdk-lzma emcmake cmake .. -DHOST_BINARY_DIR=$(pwd)/build-host -DCMAKE_BUILD_TYPE=RelWithDebInfo -DOPTION_USE_ASSERTS=OFF
+  docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build emsdk-lzma emcmake cmake .. -DHOST_BINARY_DIR=../build-host -DCMAKE_BUILD_TYPE=Release -DOPTION_USE_ASSERTS=OFF
   docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build emsdk-lzma emmake make -j5
 ```