diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 882332dffa13..98e624a830ec 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,10 @@
+2005-12-17  Steven G. Kargl  <kargls@comcast.net>
+	    Tobias Schlueter <tobias.schlueter@physik.uni-muenchen.de>
+
+	PR fortran/25458
+	* simplify.c (gfc_simplify_ibset, gfc_simplify_not): Add call to
+	twos_complement.
+
 2005-12-17  Steven G. Kargl  <kargls@comcast.net>
 
 	* decl.c (gfc_match_old_kind_spec,match_type_spec): Use gfc_std_notify
diff --git a/gcc/fortran/simplify.c b/gcc/fortran/simplify.c
index e6fbefcfe5ba..5b47e930db63 100644
--- a/gcc/fortran/simplify.c
+++ b/gcc/fortran/simplify.c
@@ -1348,6 +1348,9 @@ gfc_simplify_ibset (gfc_expr * x, gfc_expr * y)
   result = gfc_copy_expr (x);
 
   mpz_setbit (result->value.integer, pos);
+
+  twos_complement (result->value.integer, gfc_integer_kinds[k].bit_size);
+
   return range_check (result, "IBSET");
 }
 
@@ -2514,6 +2517,8 @@ gfc_simplify_not (gfc_expr * e)
   mpz_and (result->value.integer, result->value.integer,
 	   gfc_integer_kinds[i].max_int);
 
+  twos_complement (result->value.integer, gfc_integer_kinds[i].bit_size);
+
   return range_check (result, "NOT");
 }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a45284b7ecbb..b7e00b9046a7 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2005-12-17  Steven G. Kargl  <kargls@comcast.net>
+
+	* PR fortran/25458
+	* gfortran.dg/chkbits.f90: New test.
+
 2005-12-17  Steven G. Kargl  <kargls@comcast.net>
 
 	*gfortran.dg/enum_5.f:  Revert to previous version.
diff --git a/gcc/testsuite/gfortran.dg/chkbits.f90 b/gcc/testsuite/gfortran.dg/chkbits.f90
new file mode 100644
index 000000000000..19ab5c722c6e
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/chkbits.f90
@@ -0,0 +1,26 @@
+! { dg-do run }
+! NOT() was not return the two's complement value as reported by
+! PR fortran/25458.  In checking other bit manipulation intrinsics,
+! IBSET was found to be in error.
+program chkbits
+
+  implicit none
+
+  integer(kind=1) i1
+  integer(kind=2) i2
+  integer(kind=4) i4
+  integer(kind=8) i8
+
+  i1 = ibset(2147483647,bit_size(i4)-1)
+  i2 = ibset(2147483647,bit_size(i4)-1)
+  i4 = ibset(2147483647,bit_size(i4)-1)
+  i8 = ibset(2147483647,bit_size(i4)-1)
+  if (i1 /= -1 .or. i2 /= -1 .or. i4 /= -1 .or. i8 /= -1) call abort
+
+  i1 = not(0)
+  i2 = not(0)
+  i4 = not(0)
+  i8 = not(0)
+  if (i1 /= -1 .or. i2 /= -1 .or. i4 /= -1 .or. i8 /= -1) call abort
+
+end program chkbits