diff --git a/.gitignore b/.gitignore
index 5ee4ad9c0..f48014d1c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,6 +8,7 @@
 /templates/
 /configure/*.local
 /modules/RELEASE.local
+/modules/Makefile.local
 O.*/
 /QtC-*
 *.orig
diff --git a/modules/Makefile b/modules/Makefile
index 97134be1c..8bde5992c 100644
--- a/modules/Makefile
+++ b/modules/Makefile
@@ -36,8 +36,11 @@ pva2pva_DEPEND_DIRS = pvAccess
 SUBMODULES += example
 example_DEPEND_DIRS = pva2pva pvaClient
 
-# Add any checked-out submodules to DIRS
-DIRS += $(subst /,,$(dir $(wildcard $(addsuffix /Makefile, $(SUBMODULES)))))
+# Allow sites to add extra submodules
+-include Makefile.local
+
+# Add only checked-out submodules to DIRS
+DIRS += $(subst /Makefile,,$(wildcard $(addsuffix /Makefile, $(SUBMODULES))))
 
 include $(TOP)/configure/RULES_DIRS