diff --git a/Tests/RunCMake/CMakePresetsTest/RunCMakeTest.cmake b/Tests/RunCMake/CMakePresetsTest/RunCMakeTest.cmake
index 1c7b8360f7..5bd0158653 100644
--- a/Tests/RunCMake/CMakePresetsTest/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CMakePresetsTest/RunCMakeTest.cmake
@@ -1,5 +1,9 @@
 include(RunCMake)
 
+# Isolate our ctest runs from external environment.
+unset(ENV{CTEST_PARALLEL_LEVEL})
+unset(ENV{CTEST_OUTPUT_ON_FAILURE})
+
 # Presets do not support legacy VS generator name architecture suffix.
 if(RunCMake_GENERATOR MATCHES "^(Visual Studio [0-9]+ [0-9]+) ")
   set(RunCMake_GENERATOR "${CMAKE_MATCH_1}")
diff --git a/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake b/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake
index df3e82af70..8c35fe5d64 100644
--- a/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake
@@ -3,9 +3,6 @@ include(RunCTest)
 
 set(RunCMake_TEST_TIMEOUT 60)
 
-unset(ENV{CTEST_PARALLEL_LEVEL})
-unset(ENV{CTEST_OUTPUT_ON_FAILURE})
-
 run_cmake_command(repeat-opt-bad1
   ${CMAKE_CTEST_COMMAND} --repeat until-pass
   )
diff --git a/Tests/RunCMake/GoogleTest/RunCMakeTest.cmake b/Tests/RunCMake/GoogleTest/RunCMakeTest.cmake
index 695f562fb4..b494cefb8c 100644
--- a/Tests/RunCMake/GoogleTest/RunCMakeTest.cmake
+++ b/Tests/RunCMake/GoogleTest/RunCMakeTest.cmake
@@ -1,5 +1,9 @@
 include(RunCMake)
 
+# Isolate our ctest runs from external environment.
+unset(ENV{CTEST_PARALLEL_LEVEL})
+unset(ENV{CTEST_OUTPUT_ON_FAILURE})
+
 if(RunCMake_GENERATOR STREQUAL "Borland Makefiles" OR
    RunCMake_GENERATOR STREQUAL "Watcom WMake")
   set(fs_delay 3)
diff --git a/Tests/RunCMake/RunCTest.cmake b/Tests/RunCMake/RunCTest.cmake
index 59db395e1b..86f5b3a26a 100644
--- a/Tests/RunCMake/RunCTest.cmake
+++ b/Tests/RunCMake/RunCTest.cmake
@@ -1,5 +1,9 @@
 include(RunCMake)
 
+# Isolate our ctest runs from external environment.
+unset(ENV{CTEST_PARALLEL_LEVEL})
+unset(ENV{CTEST_OUTPUT_ON_FAILURE})
+
 function(run_ctest CASE_NAME)
   configure_file(${RunCMake_SOURCE_DIR}/test.cmake.in
                  ${RunCMake_BINARY_DIR}/${CASE_NAME}/test.cmake @ONLY)
diff --git a/Tests/RunCMake/ctest_environment/RunCMakeTest.cmake b/Tests/RunCMake/ctest_environment/RunCMakeTest.cmake
index 365c9e833e..4716c41205 100644
--- a/Tests/RunCMake/ctest_environment/RunCMakeTest.cmake
+++ b/Tests/RunCMake/ctest_environment/RunCMakeTest.cmake
@@ -1,9 +1,5 @@
 include(RunCTest)
 
-# Isolate our ctest runs from external environment.
-unset(ENV{CTEST_PARALLEL_LEVEL})
-unset(ENV{CTEST_OUTPUT_ON_FAILURE})
-
 set(CASE_SOURCE_DIR "${RunCMake_SOURCE_DIR}")
 set(RunCTest_VERBOSE_FLAG "-VV")
 
diff --git a/Tests/RunCMake/ctest_fixtures/RunCMakeTest.cmake b/Tests/RunCMake/ctest_fixtures/RunCMakeTest.cmake
index 17542030ef..1c2ad89577 100644
--- a/Tests/RunCMake/ctest_fixtures/RunCMakeTest.cmake
+++ b/Tests/RunCMake/ctest_fixtures/RunCMakeTest.cmake
@@ -1,9 +1,5 @@
 include(RunCTest)
 
-# Isolate our ctest runs from external environment.
-unset(ENV{CTEST_PARALLEL_LEVEL})
-unset(ENV{CTEST_OUTPUT_ON_FAILURE})
-
 function(run_ctest_test CASE_NAME)
   set(CASE_CTEST_FIXTURES_ARGS "${ARGN}")
   run_ctest(${CASE_NAME})
diff --git a/Tests/RunCMake/ctest_memcheck/RunCMakeTest.cmake b/Tests/RunCMake/ctest_memcheck/RunCMakeTest.cmake
index cb8f6963c7..3f6501efaa 100644
--- a/Tests/RunCMake/ctest_memcheck/RunCMakeTest.cmake
+++ b/Tests/RunCMake/ctest_memcheck/RunCMakeTest.cmake
@@ -4,8 +4,6 @@ set(SITE test-site)
 set(BUILDNAME test-build)
 set(COVERAGE_COMMAND "")
 
-unset(ENV{CTEST_PARALLEL_LEVEL})
-
 function(run_mc_test CASE_NAME CHECKER_COMMAND)
   run_ctest(${CASE_NAME} ${ARGN})
 endfunction()
diff --git a/Tests/RunCMake/ctest_test/RunCMakeTest.cmake b/Tests/RunCMake/ctest_test/RunCMakeTest.cmake
index 74ae99cc62..242a059600 100644
--- a/Tests/RunCMake/ctest_test/RunCMakeTest.cmake
+++ b/Tests/RunCMake/ctest_test/RunCMakeTest.cmake
@@ -1,9 +1,6 @@
 include(RunCTest)
 set(RunCMake_TEST_TIMEOUT 60)
 
-unset(ENV{CTEST_PARALLEL_LEVEL})
-unset(ENV{CTEST_OUTPUT_ON_FAILURE})
-
 set(CASE_CTEST_TEST_ARGS "")
 set(CASE_CTEST_TEST_LOAD "")
 
diff --git a/Tests/RunCMake/test_include_dirs/RunCMakeTest.cmake b/Tests/RunCMake/test_include_dirs/RunCMakeTest.cmake
index 72056aee36..74795c205b 100644
--- a/Tests/RunCMake/test_include_dirs/RunCMakeTest.cmake
+++ b/Tests/RunCMake/test_include_dirs/RunCMakeTest.cmake
@@ -1,5 +1,9 @@
 include(RunCMake)
 
+# Isolate our ctest runs from external environment.
+unset(ENV{CTEST_PARALLEL_LEVEL})
+unset(ENV{CTEST_OUTPUT_ON_FAILURE})
+
 function(run_TID)
   # Use a single build tree for a few tests without cleaning.
   set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/TID-build)