diff --git a/contrib/Filelists.cmake b/contrib/Filelists.cmake
index ce1af3d6..fc9f4741 100644
--- a/contrib/Filelists.cmake
+++ b/contrib/Filelists.cmake
@@ -8,6 +8,8 @@
 # The intention is to provide greater flexibility to users to 
 # create their own targets using the *_SRCS variables.
 
+include_guard(GLOBAL)
+
 set(lwipcontribexamples_SRCS
     ${LWIP_CONTRIB_DIR}/examples/httpd/fs_example/fs_example.c
     ${LWIP_CONTRIB_DIR}/examples/httpd/ssi_example/ssi_example.c
diff --git a/contrib/ports/CMakeCommon.cmake b/contrib/ports/CMakeCommon.cmake
index 3ef478bb..8048fa2e 100644
--- a/contrib/ports/CMakeCommon.cmake
+++ b/contrib/ports/CMakeCommon.cmake
@@ -1,3 +1,5 @@
+include_guard(GLOBAL)
+
 set(LWIP_CONTRIB_DIR ${LWIP_DIR}/contrib)
 
 # ARM mbedtls support https://tls.mbed.org/
diff --git a/contrib/ports/unix/Filelists.cmake b/contrib/ports/unix/Filelists.cmake
index 83f02956..3301dfdf 100644
--- a/contrib/ports/unix/Filelists.cmake
+++ b/contrib/ports/unix/Filelists.cmake
@@ -8,6 +8,8 @@
 # The intention is to provide greater flexibility to users to 
 # create their own targets using the *_SRCS variables.
 
+include_guard(GLOBAL)
+
 set(lwipcontribportunix_SRCS
     ${LWIP_CONTRIB_DIR}/ports/unix/port/sys_arch.c
     ${LWIP_CONTRIB_DIR}/ports/unix/port/perf.c
diff --git a/contrib/ports/win32/Filelists.cmake b/contrib/ports/win32/Filelists.cmake
index a6e6b5b5..9a05803d 100644
--- a/contrib/ports/win32/Filelists.cmake
+++ b/contrib/ports/win32/Filelists.cmake
@@ -8,6 +8,8 @@
 # The intention is to provide greater flexibility to users to 
 # create their own targets using the *_SRCS variables.
 
+include_guard(GLOBAL)
+
 set(lwipcontribportwindows_SRCS
     ${LWIP_CONTRIB_DIR}/ports/win32/sys_arch.c
     ${LWIP_CONTRIB_DIR}/ports/win32/sio.c
diff --git a/src/Filelists.cmake b/src/Filelists.cmake
index 6432950e..ef1687c7 100644
--- a/src/Filelists.cmake
+++ b/src/Filelists.cmake
@@ -8,6 +8,8 @@
 # The intention is to provide greater flexibility to users to
 # create their own targets using the *_SRCS variables.
 
+include_guard(GLOBAL)
+
 set(LWIP_VERSION_MAJOR    "2")
 set(LWIP_VERSION_MINOR    "2")
 set(LWIP_VERSION_REVISION "0")
diff --git a/test/unit/Filelists.cmake b/test/unit/Filelists.cmake
index e1f40bc9..480c4bdf 100644
--- a/test/unit/Filelists.cmake
+++ b/test/unit/Filelists.cmake
@@ -8,6 +8,8 @@
 # The intention is to provide greater flexibility to users to 
 # create their own targets using the *_SRCS variables.
 
+include_guard(GLOBAL)
+
 set(LWIP_TESTDIR ${LWIP_DIR}/test/unit)
 set(LWIP_TESTFILES
 	${LWIP_TESTDIR}/lwip_unittests.c