diff --git a/.github/workflows/docker_pygem.yml b/.github/workflows/docker_pygem.yml
index cfa3a618..53ccb5e5 100644
--- a/.github/workflows/docker_pygem.yml
+++ b/.github/workflows/docker_pygem.yml
@@ -59,6 +59,7 @@ jobs:
           no-cache: true
           file: 'docker/Dockerfile'
           build-args: |
-            PYGEM_BRANCH=${{ github.ref == 'refs/heads/master' && 'master' || 'dev' }}
+            # Map this repo's 'master' branch to 'main' in PyGEM-Community/PyGEM (upstream uses 'main')
+            PYGEM_BRANCH=${{ github.ref == 'refs/heads/master' && 'main' || 'dev' }}
           tags: |
             ghcr.io/pygem-community/pygem:${{ github.ref == 'refs/heads/master' && 'latest' || github.ref == 'refs/heads/dev' && 'dev' }}
\ No newline at end of file
diff --git a/docker/Dockerfile b/docker/Dockerfile
index 11b4dd60..ada499cd 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -16,8 +16,8 @@ WORKDIR /home/ubuntu
 # Add .local/bin to PATH
 ENV PATH="/home/ubuntu/.local/bin:${PATH}"
 
-# What PyGEM branch to clone (either master or dev; see docker_pygem.yml)
-ARG PYGEM_BRANCH=master
+# What PyGEM branch to clone (either main or dev; see docker_pygem.yml)
+ARG PYGEM_BRANCH=main
 
 RUN git clone --branch ${PYGEM_BRANCH} https://github.com/PyGEM-Community/PyGEM.git && \
     pip install --break-system-packages -e PyGEM