diff -r de5cd9217d4c -r eabf80376aab src/HOL/Number_Theory/Gauss.thy
--- a/src/HOL/Number_Theory/Gauss.thy	Sun Oct 16 09:31:03 2016 +0200
+++ b/src/HOL/Number_Theory/Gauss.thy	Sun Oct 16 09:31:04 2016 +0200
@@ -52,7 +52,7 @@
 qed
 
 lemma p_eq2: "int p = (2 * ((int p - 1) div 2)) + 1"
-  using odd_p p_ge_2 div_mult_self1_is_id [of 2 "p - 1"]   
+  using odd_p p_ge_2 nonzero_mult_div_cancel_left [of 2 "p - 1"]   
   by simp
 
 lemma p_odd_int: obtains z::int where "int p = 2*z+1" "0<z"