diff --git a/.github/actions/nss/action.yml b/.github/actions/nss/action.yml
index d470aa798e..1ef9abaa0a 100644
--- a/.github/actions/nss/action.yml
+++ b/.github/actions/nss/action.yml
@@ -16,23 +16,32 @@ inputs:
 runs:
   using: composite
   steps:
+    # Ideally, we'd use this. But things are sufficiently flaky that we're better off
+    # trying both hg and git. Leaving this here in case we want to re-try in the future.
+    #
     # - name: Checkout NSPR
     #   uses: actions/checkout@v4
     #   with:
     #     repository: "nss-dev/nspr"
     #     path: ${{ github.workspace }}/nspr
-
+    #
     # - name: Checkout NSS
     #   uses: actions/checkout@v4
     #   with:
     #     repository: "nss-dev/nss"
     #     path: ${{ github.workspace }}/nss
 
-    - run: hg clone https://hg.mozilla.org/projects/nspr ${{ github.workspace }}/nspr
+    - name: Checkout NSPR
       shell: bash
+      run: |
+        hg clone https://hg.mozilla.org/projects/nspr "${{ github.workspace }}/nspr" || \
+          git clone --depth=1 https://github.com/nss-dev/nspr "${{ github.workspace }}/nspr"
 
-    - run: hg clone https://hg.mozilla.org/projects/nss ${{ github.workspace }}/nss
+    - name: Checkout NSS
       shell: bash
+      run: |
+        hg clone https://hg.mozilla.org/projects/nss "${{ github.workspace }}/nss" || \
+          git clone --depth=1 https://github.com/nss-dev/nss "${{ github.workspace }}/nss"
 
     - name: Build
       shell: bash
diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index fc6eb0c284..e96466e2e1 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -46,7 +46,7 @@ jobs:
         env:
           DEBIAN_FRONTEND: noninteractive
         run: |
-          sudo apt-get install -y --no-install-recommends gyp ninja-build lld
+          sudo apt-get install -y --no-install-recommends gyp mercurial ninja-build lld
           echo "RUSTFLAGS=-C link-arg=-fuse-ld=lld" >> "$GITHUB_ENV"
 
       # In addition to installing dependencies, first make sure System Integrity Protection (SIP)
@@ -58,7 +58,7 @@ jobs:
         if: runner.os == 'MacOS'
         run: |
           csrutil status | grep disabled
-          brew install ninja llvm
+          brew install ninja mercurial llvm
           echo "/opt/homebrew/opt/llvm/bin" >> "$GITHUB_PATH"
           ln -s /opt/homebrew/bin/python3 /opt/homebrew/bin/python
           # python3 -m pip install gyp-next