diff --git a/Tests/RunCMake/FindPkgConfig/RunCMakeTest.cmake b/Tests/RunCMake/FindPkgConfig/RunCMakeTest.cmake
index b77bb54..7b479f1 100644
--- a/Tests/RunCMake/FindPkgConfig/RunCMakeTest.cmake
+++ b/Tests/RunCMake/FindPkgConfig/RunCMakeTest.cmake
@@ -1,5 +1,10 @@
 include(RunCMake)
 
+# Isolate test cases from caller's environment.
+set(ENV{CMAKE_PREFIX_PATH} "")
+set(ENV{CMAKE_APPBUNDLE_PATH} "")
+set(ENV{CMAKE_FRAMEWORK_PATH} "")
+
 run_cmake(FindPkgConfig_NO_PKGCONFIG_PATH)
 run_cmake(FindPkgConfig_PKGCONFIG_PATH)
 run_cmake(FindPkgConfig_PKGCONFIG_PATH_NO_CMAKE_PATH)