diff --git a/.github/workflows/ci_ubuntu.yaml b/.github/workflows/ci_ubuntu.yaml
index b586d8cd2..04d999929 100644
--- a/.github/workflows/ci_ubuntu.yaml
+++ b/.github/workflows/ci_ubuntu.yaml
@@ -25,7 +25,7 @@ jobs:
 
     env:
       boost_path: "${{ github.workspace }}/../boost"
-      harden_flags: "-D_FORTIFY_SOURCE=2 -D_GLIBCXX_ASSERTIONS"
+      harden_flags: "-D_FORTIFY_SOURCE=3 -D_GLIBCXX_ASSERTIONS"
       libtorrent_path: "${{ github.workspace }}/../libtorrent"
 
     steps: