diff --git a/.github/scripts/ubuntu/install-pkg.sh b/.github/scripts/ubuntu/install-pkg.sh
index ec85a1778d..853ea6e268 100755
--- a/.github/scripts/ubuntu/install-pkg.sh
+++ b/.github/scripts/ubuntu/install-pkg.sh
@@ -12,7 +12,6 @@ EPHEMERAL="
 	python3-pytest
 	python3-pytest-timeout
 	python3-pytest-xdist
-	valgrind
 	x11-utils
 	x11-xserver-utils
 	xauth
diff --git a/.github/workflows/build-xserver.yml b/.github/workflows/build-xserver.yml
index ebad522ace..e4acd25ede 100644
--- a/.github/workflows/build-xserver.yml
+++ b/.github/workflows/build-xserver.yml
@@ -266,6 +266,11 @@ jobs:
 
             - uses: ./.github/actions/ubuntu-install-pkg
 
+            - name: Install valgrind (separate from install-pkg to work around Ubuntu mirror races on libc6-dbg)
+              run: |
+                  sudo apt-get update
+                  sudo apt-get install -y valgrind
+
             - name: prepare build environment
               run: |
                 MACHINE=`gcc -dumpmachine`