diff --git a/tools/pybind11Common.cmake b/tools/pybind11Common.cmake
index 7afb0d0b1..69ac4b0f6 100644
--- a/tools/pybind11Common.cmake
+++ b/tools/pybind11Common.cmake
@@ -20,6 +20,7 @@ Adds the following functions::
 #]======================================================]
 
 # CMake 3.10 has an include_guard command, but we can't use that yet
+# include_guard(global) (pre-CMake 3.10)
 if(TARGET pybind11::lto)
   return()
 endif()
diff --git a/tools/pybind11NewTools.cmake b/tools/pybind11NewTools.cmake
index 0a7b84706..9e2fd2b40 100644
--- a/tools/pybind11NewTools.cmake
+++ b/tools/pybind11NewTools.cmake
@@ -5,6 +5,12 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
+if(CMAKE_VERSION VERSION_LESS 3.12)
+  message(FATAL_ERROR "You cannot use the new FindPython module with CMake < 3.12")
+endif()
+
+include_guard(GLOBAL)
+
 get_property(
   is_config
   TARGET pybind11::headers
@@ -16,10 +22,6 @@ else()
   set(_pybind11_quiet "")
 endif()
 
-if(CMAKE_VERSION VERSION_LESS 3.12)
-  message(FATAL_ERROR "You cannot use the new FindPython module with CMake < 3.12")
-endif()
-
 if(NOT Python_FOUND
    AND NOT Python3_FOUND
    AND NOT Python2_FOUND)
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index 026069c73..c255e5cfd 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -5,6 +5,11 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
+# include_guard(global) (pre-CMake 3.10)
+if(TARGET pybind11::python_headers)
+  return()
+endif()
+
 # Built-in in CMake 3.5+
 include(CMakeParseArguments)