diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9bc5f9777f..8c1fed8f97 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -69,7 +69,7 @@ jobs:
     steps:
     - uses: actions/checkout@v4
     - name: config
-      run: CPPFLAGS=-ansi ./config --banner=Configured no-asm no-makedepend enable-buildtest-c++ enable-fips --strict-warnings -D_DEFAULT_SOURCE && perl configdata.pm --dump
+      run: CPPFLAGS='-ansi -D_XOPEN_SOURCE=1 -D_POSIX_C_SOURCE=200809L' ./config --banner=Configured no-asm no-secure-memory no-makedepend enable-buildtest-c++ enable-fips --strict-warnings && perl configdata.pm --dump
     - name: make
       run: make -s -j4