diff --git a/.github/workflows/sgdk-docker.yml b/.github/workflows/sgdk-docker.yml
index ed7ffa08..e2b6025b 100644
--- a/.github/workflows/sgdk-docker.yml
+++ b/.github/workflows/sgdk-docker.yml
@@ -20,6 +20,12 @@ on:
       - 'sample/**'
       - '**.md'
 
+env:
+  # TODO: arm64 images are currently disabled because they keep hanging in the
+  # GitHub Actions environment.
+  #PLATFORMS: linux/amd64,linux/arm64
+  PLATFORMS: linux/amd64
+
 jobs:
   build:
     runs-on: ubuntu-latest
@@ -32,8 +38,10 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Set up QEMU
-        uses: docker/setup-qemu-action@v3
+      # TODO: arm64 images are currently disabled because they keep hanging in
+      # the GitHub Actions environment.
+      #- name: Set up QEMU
+      #  uses: docker/setup-qemu-action@v3
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
@@ -60,10 +68,7 @@ jobs:
         with:
           file: deps/gcc.Dockerfile
           context: deps/
-          platforms: linux/amd64,linux/arm64
-          # Disable parallel builds, which are hanging in GitHub Actions.
-          build-args: |
-            PARALLEL_BUILD=0
+          platforms: ${{ env.PLATFORMS }}
           tags: ghcr.io/${{ github.actor }}/sgdk-m68k-gcc:latest
           push: ${{ github.event_name == 'push' }}
 
@@ -80,7 +85,7 @@ jobs:
         with:
           file: Dockerfile
           context: .
-          platforms: linux/amd64,linux/arm64
+          platforms: ${{ env.PLATFORMS }}
           build-args: |
             BASE_IMAGE=ghcr.io/${{ github.actor }}/sgdk-m68k-gcc
           tags: ghcr.io/${{ github.actor }}/sgdk:latest
diff --git a/deps/gcc.Dockerfile b/deps/gcc.Dockerfile
index cb7ba12a..28299e77 100644
--- a/deps/gcc.Dockerfile
+++ b/deps/gcc.Dockerfile
@@ -29,9 +29,9 @@ ENV INSTALLDIR="$BASEDIR/install"
 ENV STAGINGDIR="$BASEDIR/staging"
 ENV PARALLEL_BUILD="$PARALLEL_BUILD"
 
-# Choose parallel build or not.  Parallel builds are hanging under qemu on
-# GitHub, so we serialize building there.  If parallel builds are disabled,
-# replace nproc so it always says "1".
+# Choose parallel build or not.  Parallel builds can cause issues with
+# low-memory hosts or emulation.  If parallel builds are disabled, replace
+# nproc so it always says "1".
 RUN echo "nproc = $(nproc)"
 RUN echo "PARALLEL_BUILD = $PARALLEL_BUILD"
 RUN if [[ "$PARALLEL_BUILD" == 0 ]]; then echo -e "#!/bin/sh\necho 1" > /usr/local/bin/nproc; chmod 755 /usr/local/bin/nproc; fi