diff -r dd58f13a8eb4 -r eb85850d3eb7 src/HOL/Library/EfficientNat.thy
--- a/src/HOL/Library/EfficientNat.thy	Fri Nov 17 02:19:55 2006 +0100
+++ b/src/HOL/Library/EfficientNat.thy	Fri Nov 17 02:20:03 2006 +0100
@@ -25,7 +25,7 @@
 *}
 
 definition
-  nat_of_int :: "int \<Rightarrow> nat"
+  nat_of_int :: "int \<Rightarrow> nat" where
   "k \<ge> 0 \<Longrightarrow> nat_of_int k = nat k"
 
 lemma nat_of_int_int: