diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index d8fdb2a..6f78332 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -12,9 +12,25 @@ concurrency:
 jobs:
   check:
     runs-on: ubuntu-24.04
+    # The runner's disk is small (the first run after P6 landed died in
+    # the linker: "No space left on device", ld killed by SIGBUS). A fresh
+    # runner gains nothing from incremental caches, and line tables keep
+    # file:line in a panic's backtrace at a fraction of full debug info.
+    env:
+      CARGO_INCREMENTAL: "0"
+      CARGO_PROFILE_DEV_DEBUG: line-tables-only
+      CARGO_PROFILE_TEST_DEBUG: line-tables-only
     steps:
       - uses: actions/checkout@v4
+      - name: Room for the build (the image ships toolchains we never use)
+        run: |
+          sudo rm -rf /usr/share/dotnet /usr/local/lib/android /opt/ghc \
+                      /opt/hostedtoolcache/CodeQL /usr/local/.ghcup
+          df -h / | tail -1
       - uses: jdx/mise-action@v2
       - name: GUI build dependencies
         run: sudo apt-get update && sudo apt-get install -y libxkbcommon-dev libgtk-3-dev
       - run: just check
+      - name: What the build used
+        if: always()
+        run: df -h / | tail -1