diff --git a/Modules/ExternalProject.cmake b/Modules/ExternalProject.cmake
index 0c73d41a2..d91627028 100644
--- a/Modules/ExternalProject.cmake
+++ b/Modules/ExternalProject.cmake
@@ -113,6 +113,8 @@ Create custom targets to build projects in external trees
     overcome command line length limits.
     These arguments are :command:`set` using the ``FORCE`` argument,
     and therefore cannot be changed by the user.
+    Arguments may use
+    :manual:`generator expressions <cmake-generator-expressions(7)>`.
   ``CMAKE_CACHE_DEFAULT_ARGS <arg>...``
     Initial default cache arguments, of the form ``-Dvar:string=on``.
     These arguments are written in a pre-load a script that populates
@@ -121,6 +123,8 @@ Create custom targets to build projects in external trees
     These arguments can be used as default value that will be set if no
     previous value is found in the cache, and that the user can change
     later.
+    Arguments may use
+    :manual:`generator expressions <cmake-generator-expressions(7)>`.
 
   Build step options are:
 
@@ -1126,10 +1130,7 @@ function(_ep_write_initial_cache target_name script_filename script_initial_cach
   # Replace location tags.
   _ep_replace_location_tags(${target_name} script_initial_cache)
   # Write out the initial cache file to the location specified.
-  if(NOT EXISTS "${script_filename}.in")
-    file(WRITE "${script_filename}.in" "\@script_initial_cache\@\n")
-  endif()
-  configure_file("${script_filename}.in" "${script_filename}")
+  file(GENERATE OUTPUT "${script_filename}" CONTENT "${script_initial_cache}")
 endfunction()
 
 
@@ -2054,7 +2055,7 @@ function(_ep_add_configure_command name)
     get_property(cmake_cache_default_args TARGET ${name} PROPERTY _EP_CMAKE_CACHE_DEFAULT_ARGS)
 
     if(cmake_cache_args OR cmake_cache_default_args)
-      set(_ep_cache_args_script "${tmp_dir}/${name}-cache.cmake")
+      set(_ep_cache_args_script "${tmp_dir}/${name}-cache-$<CONFIG>.cmake")
       if(cmake_cache_args)
         _ep_command_line_to_initial_cache(script_initial_cache_force "${cmake_cache_args}" 1)
       endif()
diff --git a/Tests/RunCMake/ExternalProject/CMAKE_CACHE_ARGS-check.cmake b/Tests/RunCMake/ExternalProject/CMAKE_CACHE_ARGS-check.cmake
index c1e42043d..c350a63fc 100644
--- a/Tests/RunCMake/ExternalProject/CMAKE_CACHE_ARGS-check.cmake
+++ b/Tests/RunCMake/ExternalProject/CMAKE_CACHE_ARGS-check.cmake
@@ -1,4 +1,4 @@
-set(_cache_file "${RunCMake_TEST_BINARY_DIR}/tmp/FOO-cache.cmake")
+set(_cache_file "${RunCMake_TEST_BINARY_DIR}/tmp/FOO-cache-Debug.cmake")
 
 if(NOT EXISTS "${_cache_file}")
   set(RunCMake_TEST_FAILED "Initial cache not created")
diff --git a/Tests/RunCMake/ExternalProject/CMAKE_CACHE_ARGS.cmake b/Tests/RunCMake/ExternalProject/CMAKE_CACHE_ARGS.cmake
index 5e37eece6..62b164040 100644
--- a/Tests/RunCMake/ExternalProject/CMAKE_CACHE_ARGS.cmake
+++ b/Tests/RunCMake/ExternalProject/CMAKE_CACHE_ARGS.cmake
@@ -1,5 +1,8 @@
+if(NOT CMAKE_CONFIGURATION_TYPES)
+  set(CMAKE_BUILD_TYPE Debug)
+endif()
 include(ExternalProject)
 
 ExternalProject_Add(FOO TMP_DIR "${CMAKE_CURRENT_BINARY_DIR}/tmp"
                         DOWNLOAD_COMMAND ""
-                        CMAKE_CACHE_ARGS "-DFOO:STRING=BAR")
+                        CMAKE_CACHE_ARGS "-DFOO:STRING=$<1:BAR>$<0:BAD>")
diff --git a/Tests/RunCMake/ExternalProject/CMAKE_CACHE_DEFAULT_ARGS-check.cmake b/Tests/RunCMake/ExternalProject/CMAKE_CACHE_DEFAULT_ARGS-check.cmake
index ec1cafb1e..aeee11fa0 100644
--- a/Tests/RunCMake/ExternalProject/CMAKE_CACHE_DEFAULT_ARGS-check.cmake
+++ b/Tests/RunCMake/ExternalProject/CMAKE_CACHE_DEFAULT_ARGS-check.cmake
@@ -1,4 +1,4 @@
-set(_cache_file "${RunCMake_TEST_BINARY_DIR}/tmp/FOO-cache.cmake")
+set(_cache_file "${RunCMake_TEST_BINARY_DIR}/tmp/FOO-cache-Debug.cmake")
 
 if(NOT EXISTS "${_cache_file}")
   set(RunCMake_TEST_FAILED "Initial cache not created")
diff --git a/Tests/RunCMake/ExternalProject/CMAKE_CACHE_DEFAULT_ARGS.cmake b/Tests/RunCMake/ExternalProject/CMAKE_CACHE_DEFAULT_ARGS.cmake
index 8e984706b..3a83dbe38 100644
--- a/Tests/RunCMake/ExternalProject/CMAKE_CACHE_DEFAULT_ARGS.cmake
+++ b/Tests/RunCMake/ExternalProject/CMAKE_CACHE_DEFAULT_ARGS.cmake
@@ -1,5 +1,8 @@
+if(NOT CMAKE_CONFIGURATION_TYPES)
+  set(CMAKE_BUILD_TYPE Debug)
+endif()
 include(ExternalProject)
 
 ExternalProject_Add(FOO TMP_DIR "${CMAKE_CURRENT_BINARY_DIR}/tmp"
                         DOWNLOAD_COMMAND ""
-                        CMAKE_CACHE_DEFAULT_ARGS "-DFOO:STRING=BAR")
+                        CMAKE_CACHE_DEFAULT_ARGS "-DFOO:STRING=$<1:BAR>$<0:BAD>")
diff --git a/Tests/RunCMake/ExternalProject/CMAKE_CACHE_mix-check.cmake b/Tests/RunCMake/ExternalProject/CMAKE_CACHE_mix-check.cmake
index 2a07f27e5..04d49b9e4 100644
--- a/Tests/RunCMake/ExternalProject/CMAKE_CACHE_mix-check.cmake
+++ b/Tests/RunCMake/ExternalProject/CMAKE_CACHE_mix-check.cmake
@@ -1,4 +1,4 @@
-set(_cache_file "${RunCMake_TEST_BINARY_DIR}/tmp/FOO-cache.cmake")
+set(_cache_file "${RunCMake_TEST_BINARY_DIR}/tmp/FOO-cache-Debug.cmake")
 
 if(NOT EXISTS "${_cache_file}")
   set(RunCMake_TEST_FAILED "Initial cache not created")
diff --git a/Tests/RunCMake/ExternalProject/CMAKE_CACHE_mix.cmake b/Tests/RunCMake/ExternalProject/CMAKE_CACHE_mix.cmake
index e7f26ae0a..192776ba7 100644
--- a/Tests/RunCMake/ExternalProject/CMAKE_CACHE_mix.cmake
+++ b/Tests/RunCMake/ExternalProject/CMAKE_CACHE_mix.cmake
@@ -1,6 +1,9 @@
+if(NOT CMAKE_CONFIGURATION_TYPES)
+  set(CMAKE_BUILD_TYPE Debug)
+endif()
 include(ExternalProject)
 
 ExternalProject_Add(FOO TMP_DIR "${CMAKE_CURRENT_BINARY_DIR}/tmp"
                         DOWNLOAD_COMMAND ""
-                        CMAKE_CACHE_ARGS "-DFOO:STRING=BAR"
-                        CMAKE_CACHE_DEFAULT_ARGS "-DBAR:STRING=BAZ")
+                        CMAKE_CACHE_ARGS "-DFOO:STRING=$<1:BAR>$<0:BAD>"
+                        CMAKE_CACHE_DEFAULT_ARGS "-DBAR:STRING=$<1:BAZ>$<0:BAD>")