diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 375fda0970..bb097367c5 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -26,7 +26,7 @@
 
 include: 'https://gitlab.gnome.org/GNOME/citemplates/raw/master/flatpak/flatpak_ci_initiative.yml'
 
-image: debian:testing
+image: debian:bookworm
 
 stages:
   - prepare
@@ -67,7 +67,7 @@ build-image:
     - export container=docker
     - mkdir -p /kaniko/.docker
     - echo "{\"auths\":{\"$CI_REGISTRY\":{\"username\":\"$CI_REGISTRY_USER\",\"password\":\"$CI_REGISTRY_PASSWORD\"}}}" > /kaniko/.docker/config.json
-    - echo "FROM debian:testing" > Dockerfile
+    - echo "FROM debian:bookworm" > Dockerfile
     - echo "RUN apt-get update" >> Dockerfile
     - echo "RUN apt-get install -y --no-install-recommends \\" >> Dockerfile
     - echo "appstream
@@ -224,7 +224,7 @@ build-image-win32:
     - /kaniko/executor --context $CI_PROJECT_DIR --dockerfile $CI_PROJECT_DIR/Dockerfile --destination $CI_REGISTRY_IMAGE:build-win32-latest --cache=true --cache-ttl=120h
 
 
-## GNU/Linux 64-bit CIs (Debian testing) ##
+## GNU/Linux 64-bit CIs (Debian bookworm) ##
 
 deps-debian:
   rules:
diff --git a/devel-docs/os-support.txt b/devel-docs/os-support.txt
index 93acf3ba83..89669881f5 100644
--- a/devel-docs/os-support.txt
+++ b/devel-docs/os-support.txt
@@ -9,7 +9,11 @@ developers maintaining GIMP for this platform will decide.
 
 ### GNU/Linux, *BSD…
 
-Minimum dependency versions can be bumped if available in Debian Testing.
+Until GIMP 3.0 release, Debian 12 "bookworm" stable will be our baseline target.
+I.e. that we can bump a minimum dependency version only if it is in Debian
+bookworm.
+
+After GIMP 3.0 release, we might get back to depend on Debian Testing.
 
 ### macOS