diff -r a03462cbf86f -r 7641e8d831d2 src/HOL/Power.thy
--- a/src/HOL/Power.thy	Thu Feb 18 13:29:59 2010 -0800
+++ b/src/HOL/Power.thy	Thu Feb 18 14:21:44 2010 -0800
@@ -332,7 +332,7 @@
 
 lemma abs_power_minus [simp]:
   "abs ((-a) ^ n) = abs (a ^ n)"
-  by (simp add: abs_minus_cancel power_abs) 
+  by (simp add: power_abs)
 
 lemma zero_less_power_abs_iff [simp, noatp]:
   "0 < abs a ^ n \<longleftrightarrow> a \<noteq> 0 \<or> n = 0"