diff --git a/Tests/RunCMake/install/RunCMakeTest.cmake b/Tests/RunCMake/install/RunCMakeTest.cmake
index 0439b42ef4..7b0aa85225 100644
--- a/Tests/RunCMake/install/RunCMakeTest.cmake
+++ b/Tests/RunCMake/install/RunCMakeTest.cmake
@@ -8,7 +8,9 @@ function(run_install_test case)
   file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}")
   file(MAKE_DIRECTORY "${RunCMake_TEST_BINARY_DIR}")
   run_cmake(${case})
+  set(RunCMake_TEST_OUTPUT_MERGE 1)
   run_cmake_command(${case}-build ${CMAKE_COMMAND} --build . --config Debug)
+  unset(RunCMake_TEST_OUTPUT_MERGE)
   # Check "all" components.
   set(CMAKE_INSTALL_PREFIX ${RunCMake_TEST_BINARY_DIR}/root-all)
   run_cmake_command(${case}-all ${CMAKE_COMMAND} -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX} -DBUILD_TYPE=Debug -P cmake_install.cmake)