diff --git a/CMakeModules/FindDepotTools.cmake b/CMakeModules/FindDepotTools.cmake
index c23d4eb..6b2c258 100644
--- a/CMakeModules/FindDepotTools.cmake
+++ b/CMakeModules/FindDepotTools.cmake
@@ -1,3 +1,8 @@
+if(FIND_DEPOT_TOOLS_INCLUDED)
+  return()
+endif(FIND_DEPOT_TOOLS_INCLUDED)
+set(FIND_DEPOT_TOOLS_INCLUDED true)
+
 find_program(GCLIENT_EXECUTABLE
              NAMES gclient gclient.bat
              DOC "Path to gclient executable"
diff --git a/CMakeModules/FindLibraries.cmake b/CMakeModules/FindLibraries.cmake
index 20e15ba..761aa9b 100644
--- a/CMakeModules/FindLibraries.cmake
+++ b/CMakeModules/FindLibraries.cmake
@@ -1,3 +1,8 @@
+if(FIND_LIBRARIES_INCLUDED)
+  return()
+endif(FIND_LIBRARIES_INCLUDED)
+set(FIND_LIBRARIES_INCLUDED true)
+
 #
 # Find required packages
 list(APPEND LIBWEBRTC_LIBRARIES webrtc)
diff --git a/CMakeModules/GClientConfig.cmake b/CMakeModules/GClientConfig.cmake
index 818abac..1d5d458 100644
--- a/CMakeModules/GClientConfig.cmake
+++ b/CMakeModules/GClientConfig.cmake
@@ -1,3 +1,8 @@
+if(GCLIENT_CONFIG_INCLUDED)
+  return()
+endif(GCLIENT_CONFIG_INCLUDED)
+set(GCLIENT_CONFIG_INCLUDED true)
+
 #
 # Retrieve WebRTC source code
 #
@@ -22,4 +27,4 @@ elseif (TARGET_OS STREQUAL "mac")
   file(APPEND ${CMAKE_BINARY_DIR}/.gclient "target_os = [\"mac\"]")
 elseif (TARGET_OS STREQUAL "win")
   file(APPEND ${CMAKE_BINARY_DIR}/.gclient "target_os = [\"win\"]")
-endif (TARGET_OS STREQUAL "android")
\ No newline at end of file
+endif (TARGET_OS STREQUAL "android")
diff --git a/CMakeModules/Install.cmake b/CMakeModules/Install.cmake
index ca077c5..8924fcc 100644
--- a/CMakeModules/Install.cmake
+++ b/CMakeModules/Install.cmake
@@ -1,3 +1,8 @@
+if(INSTALL_INCLUDED)
+  return()
+endif(INSTALL_INCLUDED)
+set(INSTALL_INCLUDED true)
+
 #
 # Install library
 file(GLOB_RECURSE _LIBRARY_FILES
diff --git a/CMakeModules/LibWebRTCCommand.cmake b/CMakeModules/LibWebRTCCommand.cmake
index 48c73e4..b7f7e1f 100644
--- a/CMakeModules/LibWebRTCCommand.cmake
+++ b/CMakeModules/LibWebRTCCommand.cmake
@@ -1,3 +1,8 @@
+if(LIBWEBRTC_COMMAND_INCLUDED)
+  return()
+endif(LIBWEBRTC_COMMAND_INCLUDED)
+set(LIBWEBRTC_COMMAND_INCLUDED true)
+
 include(CMakeParseArguments)
 include(Prefix)
 
diff --git a/CMakeModules/Options.cmake b/CMakeModules/Options.cmake
index 65c3e7d..219bc3b 100644
--- a/CMakeModules/Options.cmake
+++ b/CMakeModules/Options.cmake
@@ -1,3 +1,8 @@
+if(OPTIONS_INCLUDED)
+  return()
+endif(OPTIONS_INCLUDED)
+set(OPTIONS_INCLUDED true)
+
 #
 # Options, flags
 option(BUILD_TESTS "Build test binaries" OFF)
diff --git a/CMakeModules/Package.cmake b/CMakeModules/Package.cmake
index 949e6e4..7b949c3 100644
--- a/CMakeModules/Package.cmake
+++ b/CMakeModules/Package.cmake
@@ -1,3 +1,8 @@
+if(PACKAGE_INCLUDED)
+  return()
+endif(PACKAGE_INCLUDED)
+set(PACKAGE_INCLUDED true)
+
 #
 # Create package
 set(CPACK_PACKAGE_FILE_NAME "libwebrtc-${LIBWEBRTC_VERSION}-${TARGET_OS}-${TARGET_CPU}")
diff --git a/CMakeModules/Prefix.cmake b/CMakeModules/Prefix.cmake
index 3d3dcd8..f1b766b 100644
--- a/CMakeModules/Prefix.cmake
+++ b/CMakeModules/Prefix.cmake
@@ -1,3 +1,8 @@
+if(PREFIX_INCLUDED)
+  return()
+endif(PREFIX_INCLUDED)
+set(PREFIX_INCLUDED true)
+
 #
 # Generate environment variables
 #
diff --git a/CMakeModules/TargetOsAndCpu.cmake b/CMakeModules/TargetOsAndCpu.cmake
index bedcffc..20bd4d9 100644
--- a/CMakeModules/TargetOsAndCpu.cmake
+++ b/CMakeModules/TargetOsAndCpu.cmake
@@ -1,3 +1,8 @@
+if(TARGET_OS_AND_CPU_INCLUDED)
+  return()
+endif(TARGET_OS_AND_CPU_INCLUDED)
+set(TARGET_OS_AND_CPU_INCLUDED true)
+
 include(CheckSymbolExists)
 
 #
@@ -82,4 +87,4 @@ elseif (WIN32)
   set(LIBWEBRTC_REQUIRED_CXX_FLAGS_DEBUG "/MTd")
   set(LIBWEBRTC_REQUIRED_CXX_FLAGS_RELEASE "/MT")
   list(APPEND LIBWEBRTC_DEFINITIONS WEBRTC_WIN NOMINMAX _CRT_SECURE_NO_WARNINGS)
-endif(UNIX)
\ No newline at end of file
+endif(UNIX)
diff --git a/CMakeModules/Version.cmake b/CMakeModules/Version.cmake
index 8840f42..d0706ff 100644
--- a/CMakeModules/Version.cmake
+++ b/CMakeModules/Version.cmake
@@ -1,3 +1,8 @@
+if(VERSION_INCLUDED)
+  return()
+endif(VERSION_INCLUDED)
+set(VERSION_INCLUDED true)
+
 #
 # Set the project's version