diff --git a/mozilla/config/rules.mak b/mozilla/config/rules.mak
index a620a02518a..895f553a7f0 100644
--- a/mozilla/config/rules.mak
+++ b/mozilla/config/rules.mak
@@ -481,7 +481,7 @@ unmangle:: $(DIRS)
 
 alltags::
         echo Making emacs tags
-	c:\\mksnt\\find . -name dist -prune -o ( -name '*.[hc]' -o -name '*.cpp' ) -print | c:\\mksnt\\xargs etags -a
+	c:\\mksnt\\find . -name dist -prune -o ( -name '*.[hc]' -o -name '*.cpp' -o -name '*.idl' ) -print | c:\\mksnt\\xargs etags -a
 
 
 #//------------------------------------------------------------------------
diff --git a/mozilla/config/rules.mk b/mozilla/config/rules.mk
index 6723aa707d6..28ff3269dc3 100644
--- a/mozilla/config/rules.mk
+++ b/mozilla/config/rules.mk
@@ -419,7 +419,7 @@ distclean::
 
 alltags:
 	rm -f TAGS
-	find . -name dist -prune -o \( -name '*.[hc]' -o -name '*.cp' -o -name '*.cpp' \) -print | xargs etags -a
+	find . -name dist -prune -o \( -name '*.[hc]' -o -name '*.cp' -o -name '*.cpp' -o -name '*.idl' \) -print | xargs etags -a
 
 #
 # Turn on C++ linking if we have any .cpp files