diff --git a/make/common/MakeIncludeEnd.gmk b/make/common/MakeIncludeEnd.gmk
index 7023a861fa1..47be7c65c72 100644
--- a/make/common/MakeIncludeEnd.gmk
+++ b/make/common/MakeIncludeEnd.gmk
@@ -27,10 +27,15 @@
 # MakeIncludeEnd.gmk should be included last of all in all include files
 ################################################################################
 
-# Hook to include the corresponding custom file, if present.
-ifneq ($(NO_CUSTOM_EXTENSIONS), true)
-  CUSTOM_POST_NAME := $(subst .gmk,-post.gmk, $(THIS_INCLUDE))
-  $(eval $(call IncludeCustomExtension, $(CUSTOM_POST_NAME)))
+ifneq ($(INCLUDE_GUARD_$(THIS_INCLUDE)), true)
+  # This was the first time this file was included. Prevent future inclusion.
+  INCLUDE_GUARD_$(THIS_INCLUDE) := true
+
+  # Hook to include the corresponding custom file, if present.
+  ifneq ($(NO_CUSTOM_EXTENSIONS), true)
+    CUSTOM_POST_NAME := $(subst .gmk,-post.gmk, $(THIS_INCLUDE))
+    $(eval $(call IncludeCustomExtension, $(CUSTOM_POST_NAME)))
+  endif
 endif
 
 # Pop our helper name off the stack
diff --git a/make/common/MakeIncludeStart.gmk b/make/common/MakeIncludeStart.gmk
index 3904633f9f2..f1d690ddb41 100644
--- a/make/common/MakeIncludeStart.gmk
+++ b/make/common/MakeIncludeStart.gmk
@@ -70,7 +70,6 @@ INCLUDE_STACK := $(THIS_INCLUDE) $(INCLUDE_STACK)
 
 # Setup an automatic include guard
 ifneq ($(INCLUDE_GUARD_$(THIS_INCLUDE)), true)
-  INCLUDE_GUARD_$(THIS_INCLUDE) := true
   INCLUDE := true
 
   # Hook to include the corresponding custom file, if present.