diff --git a/.github/workflows/cpp.yml b/.github/workflows/cpp.yml
index d670501cb3c8e..8f4702dacb6b3 100644
--- a/.github/workflows/cpp.yml
+++ b/.github/workflows/cpp.yml
@@ -271,8 +271,11 @@ jobs:
         uses: actions/cache@v2
         with:
           path: ${{ steps.ccache-info.outputs.cache-dir }}
-          key: cpp-ccache-windows-v2-${{ hashFiles('cpp/**') }}
-          restore-keys: cpp-ccache-windows-v2-
+          key: cpp-ccache-windows-${{ env.CACHE_VERSION }}-${{ hashFiles('cpp/**') }}
+          restore-keys: cpp-ccache-windows-${{ env.CACHE_VERSION }}-
+        env:
+          # We can invalidate the current cache by updating this.
+          CACHE_VERSION: "2022-09-13"
       - name: Build
         shell: cmd
         run: |
diff --git a/r/src/Makevars.ucrt b/r/src/Makevars.ucrt
index 52488eb2b858e..a91dedc2d559d 100644
--- a/r/src/Makevars.ucrt
+++ b/r/src/Makevars.ucrt
@@ -17,3 +17,6 @@
 
 CRT=-ucrt
 include Makevars.win
+
+# XXX for some reason, this variable doesn't seem propagated from Makevars.win
+CXX_STD=CXX17