diff -Naur mpfr-2.1.1-p3/pow_ui.c mpfr-2.1.1-p4/pow_ui.c
--- mpfr-2.1.1-p3/pow_ui.c	2004-02-23 09:43:29.000000000 +0000
+++ mpfr-2.1.1-p4/pow_ui.c	2005-03-30 14:09:16.299081000 +0000
@@ -1,7 +1,8 @@
 /* mpfr_pow_ui-- compute the power of a floating-point
                                   by a machine integer
 
-Copyright 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
+Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2005
+ Free Software Foundation, Inc.
 
 This file is part of the MPFR Library.
 
@@ -61,6 +62,10 @@
           MPFR_ASSERTD(MPFR_IS_ZERO(y));
           /* 0^n = 0 for any n */
 	  MPFR_SET_ZERO(x);
+          if (MPFR_IS_POS (y) || ((n & 1) == 0))
+            MPFR_SET_POS (x);
+          else
+            MPFR_SET_NEG (x);
 	  MPFR_RET(0);
 	}
     }
@@ -91,7 +96,7 @@
         ;
       mpfr_set_prec (res, prec);
       inexact = mpfr_set (res, y, rnd1);
-      err = prec <= (mpfr_prec_t) i ? 0 : prec - (mpfr_prec_t) i;
+      err = prec <= (mpfr_prec_t) i ? 0 : prec - 1 - (mpfr_prec_t) i;
       MPFR_ASSERTD (i >= 1);
       /* now 2^(i-1) <= n < 2^i */
       for (i -= 2; i >= 0; i--)
diff -Naur mpfr-2.1.1-p3/tests/tpow.c mpfr-2.1.1-p4/tests/tpow.c
--- mpfr-2.1.1-p3/tests/tpow.c	2005-01-27 17:34:39.000000000 +0000
+++ mpfr-2.1.1-p4/tests/tpow.c	2005-03-30 14:08:33.308980000 +0000
@@ -84,6 +84,22 @@
       exit (1);
     }
 
+  mpfr_set_prec (a, 29);
+  mpfr_set_prec (b, 29);
+  mpfr_set_str_binary (a, "1.0000000000000000000000001111");
+  mpfr_set_str_binary (b, "1.1001101111001100111001010111e165");
+  mpfr_pow_ui (a, a, 2055225053, GMP_RNDZ);
+  if (mpfr_cmp (a, b) != 0)
+    {
+      printf ("Error for x^2055225053\n");
+      printf ("Expected ");
+      mpfr_out_str (stdout, 2, 0, b, GMP_RNDN);
+      printf ("\nGot      ");
+      mpfr_out_str (stdout, 2, 0, a, GMP_RNDN);
+      printf ("\n");
+      exit (1);
+    }
+
   mpfr_clear (a);
   mpfr_clear (b);
 }