diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 8dabd34c82..21c2d219dd 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -86,7 +86,7 @@ jobs:
           if [ '${{ matrix.build }}' = 'cmake' ]; then
             PATH="/usr/bin:$(cygpath "${SYSTEMROOT}")/System32"
             cmake -B bld -G Ninja ${options} \
-              -DCMAKE_UNITY_BUILD=ON -DCURL_TEST_BUNDLES=ON \
+              -DCMAKE_UNITY_BUILD=ON -DCMAKE_UNITY_BUILD_BATCH_SIZE=32 -DCURL_TEST_BUNDLES=ON \
               -DCURL_WERROR=ON \
               ${{ matrix.config }}
           else
@@ -252,7 +252,7 @@ jobs:
             cmake -B bld -G Ninja ${options} \
               -DCMAKE_C_FLAGS="${{ matrix.cflags }} ${CFLAGS_CMAKE} ${CPPFLAGS}" \
               -DCMAKE_BUILD_TYPE='${{ matrix.type }}' \
-              -DCMAKE_UNITY_BUILD=ON -DCURL_TEST_BUNDLES=ON \
+              -DCMAKE_UNITY_BUILD=ON -DCMAKE_UNITY_BUILD_BATCH_SIZE=32 -DCURL_TEST_BUNDLES=ON \
               -DCURL_WERROR=ON \
               ${{ matrix.config }}
           else
@@ -438,7 +438,7 @@ jobs:
           cmake -B bld -G 'MSYS Makefiles' ${options} \
             -DCMAKE_C_COMPILER=gcc \
             -DCMAKE_BUILD_TYPE='${{ matrix.type }}' \
-            -DCMAKE_UNITY_BUILD=ON -DCURL_TEST_BUNDLES=ON \
+            -DCMAKE_UNITY_BUILD=ON -DCMAKE_UNITY_BUILD_BATCH_SIZE=30 -DCURL_TEST_BUNDLES=ON \
             -DCURL_WERROR=ON \
             -DCURL_USE_LIBPSL=OFF \
             ${{ matrix.config }}
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index 168fa20cf3..5f1b395f0a 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -55,6 +55,9 @@ if(CURL_BUILD_TESTING)
   )
   target_compile_definitions(curlu PUBLIC "UNITTESTS" "CURL_STATICLIB")
   target_link_libraries(curlu PRIVATE ${CURL_LIBS})
+  # There is plenty of parallelism when building the testdeps target.
+  # Override the curlu batch size with the maximum to optimize performance.
+  set_target_properties(curlu PROPERTIES UNITY_BUILD_BATCH_SIZE 0)
 endif()
 
 if(ENABLE_CURLDEBUG)