diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 3bebe41e..7603dcf8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -103,7 +103,13 @@ jobs:
       - name: Build with nullable warnings treated as errors
         shell: pwsh
         run: |
-          & msbuild $env:SOLUTION_PATH /t:Build /m /p:Configuration=Debug `
+          # Use /t:Rebuild (not /t:Build) so this step always performs a genuine full
+          # recompile under /p:Nullable=enable. The preceding "Build with analyzers"
+          # step already compiled everything under the projects' own Nullable settings;
+          # MSBuild's incremental up-to-date check does not invalidate on a changed
+          # -p:Nullable command-line property alone, so a plain /t:Build here would
+          # silently skip recompilation and never actually enforce this gate.
+          & msbuild $env:SOLUTION_PATH /t:Rebuild /m /p:Configuration=Debug `
               "/p:Platform=Any CPU" `
               /p:Nullable=enable /p:TreatWarningsAsErrors=true
           if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }