diff --git a/Tests/CMakeTests/CheckSourceTreeTest.cmake.in b/Tests/CMakeTests/CheckSourceTreeTest.cmake.in
index 33fe5f3f8..8145db7cb 100644
--- a/Tests/CMakeTests/CheckSourceTreeTest.cmake.in
+++ b/Tests/CMakeTests/CheckSourceTreeTest.cmake.in
@@ -16,8 +16,13 @@ string(REPLACE "\\" "\\\\" HOME "${HOME}")
 # (i.e. - is it an "in source" build?)
 #
 set(in_source_build 0)
+set(build_under_source 0)
 
-if(CMake_SOURCE_DIR STREQUAL "${CMake_BINARY_DIR}")
+string(FIND "${CMake_BINARY_DIR}" "${CMake_SOURCE_DIR}/" pos)
+if(pos EQUAL 0)
+  message("build dir is *inside* source dir")
+  set(build_under_source 1)
+elseif(CMake_SOURCE_DIR STREQUAL "${CMake_BINARY_DIR}")
   message("build dir *is* source dir")
   set(in_source_build 1)
 else()
@@ -39,8 +44,13 @@ message("bin_len='${bin_len}'")
 message("substr_len='${substr_len}'")
 message("bin_dir='${bin_dir}'")
 message("in_source_build='${in_source_build}'")
+message("build_under_source='${build_under_source}'")
 message("")
 
+if(build_under_source)
+  message(STATUS "Skipping rest of test because build tree is under source tree")
+  return()
+endif()
 
 # If this does not appear to be a git checkout, just pass the test here
 # and now. (Do not let the test fail if it is run in a tree *exported* from a
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)