diff --git a/Tests/FindPackageTest/CMakeLists.txt b/Tests/FindPackageTest/CMakeLists.txt
index 8fafa3b70..fadd0feef 100644
--- a/Tests/FindPackageTest/CMakeLists.txt
+++ b/Tests/FindPackageTest/CMakeLists.txt
@@ -1,6 +1,9 @@
 cmake_minimum_required (VERSION 2.6)
 project(FindPackageTest)
 
+# Protect tests from running inside the default install prefix.
+set(CMAKE_INSTALL_PREFIX "${CMAKE_CURRENT_BINARY_DIR}/NotDefaultPrefix")
+
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR})
 
 # Look for a package which uses FindPackageHandleStandardArgs.cmake with the
diff --git a/Tests/RunCMake/CMP0041/RunCMakeTest.cmake b/Tests/RunCMake/CMP0041/RunCMakeTest.cmake
index a5e2114cb..e7f27a1a2 100644
--- a/Tests/RunCMake/CMP0041/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CMP0041/RunCMakeTest.cmake
@@ -1,5 +1,8 @@
 include(RunCMake)
 
+# Protect tests from running inside the default install prefix.
+set(RunCMake_TEST_OPTIONS "-DCMAKE_INSTALL_PREFIX=${RunCMake_BINARY_DIR}/NotDefaultPrefix")
+
 run_cmake(CMP0041-OLD)
 run_cmake(CMP0041-NEW)
 run_cmake(CMP0041-WARN)
diff --git a/Tests/RunCMake/IfacePaths/RunCMakeTest.cmake b/Tests/RunCMake/IfacePaths/RunCMakeTest.cmake
index 489e3dfbf..066c83e63 100644
--- a/Tests/RunCMake/IfacePaths/RunCMakeTest.cmake
+++ b/Tests/RunCMake/IfacePaths/RunCMakeTest.cmake
@@ -6,6 +6,9 @@ macro(run_cmake test)
   _run_cmake(${test})
 endmacro()
 
+# Protect tests from running inside the default install prefix.
+set(RunCMake_TEST_OPTIONS "-DCMAKE_INSTALL_PREFIX=${RunCMake_BINARY_DIR}/NotDefaultPrefix")
+
 run_cmake(RelativePathInInterface)
 run_cmake(RelativePathInGenex)
 run_cmake(export-NOWARN)
diff --git a/Tests/RunCMake/include_directories/RunCMakeTest.cmake b/Tests/RunCMake/include_directories/RunCMakeTest.cmake
index 3f624f850..54d5e9773 100644
--- a/Tests/RunCMake/include_directories/RunCMakeTest.cmake
+++ b/Tests/RunCMake/include_directories/RunCMakeTest.cmake
@@ -1,5 +1,8 @@
 include(RunCMake)
 
+# Protect tests from running inside the default install prefix.
+set(RunCMake_TEST_OPTIONS "-DCMAKE_INSTALL_PREFIX=${RunCMake_BINARY_DIR}/NotDefaultPrefix")
+
 run_cmake(NotFoundContent)
 run_cmake(DebugIncludes)
 run_cmake(TID-bad-target)