diff --git a/.gitignore b/.gitignore
index 3e6f4d458f..e9da0c6a71 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,8 @@
 *Theory.sig
 *Theory.sml
 *Theory.dat
+!Theory.sig
+!Theory.sml
 *.uo
 *.ui
 *.o