diff --git a/.github/workflows/snapshot-on-push-master.yml b/.github/workflows/snapshot-on-push-master.yml
index 769d778d5..192468079 100644
--- a/.github/workflows/snapshot-on-push-master.yml
+++ b/.github/workflows/snapshot-on-push-master.yml
@@ -75,13 +75,13 @@ jobs:
       - name: Build and package 64-bit Windows versions of the tools.
         run: |
           make -C src clean
-          make -j2 bin USER_CFLAGS=-Werror CROSS_COMPILE=x86_64-w64-mingw32-
+          make -j2 bin USER_CFLAGS="-D __STDC_FORMAT_MACROS -Werror" CROSS_COMPILE=x86_64-w64-mingw32-
           make zip
           mv cc65.zip cc65-snapshot-win64.zip
       - name: Build and package 32-bit Windows versions of the tools.
         run: |
           make -C src clean
-          make -j2 bin USER_CFLAGS=-Werror CROSS_COMPILE=i686-w64-mingw32-
+          make -j2 bin USER_CFLAGS="-D __STDC_FORMAT_MACROS -Werror" CROSS_COMPILE=i686-w64-mingw32-
           make zip
           mv cc65.zip cc65-snapshot-win32.zip