diff --git a/gambit-c.spec b/gambit-c.spec
index a1b96ad..77fd6c0 100644
--- a/gambit-c.spec
+++ b/gambit-c.spec
@@ -1,12 +1,20 @@
 %global dirname gambc-v4_6_5-devel
 
-# ppc64 support is broken at the moment.
-# use with --with ppc64 to test
-%bcond_with ppc64
+# Using -O2 on ppc64 triggers ICE with gcc
+# http://www.iro.umontreal.ca/~gambit/bugzilla/show_bug.cgi?id=155
+# https://bugzilla.redhat.com/show_bug.cgi?id=808285
+# Use --with ppc64opt2 when rebuilding to see if this is fixed
+%bcond_with ppc64opt2
+
+%ifarch ppc64
+%if ! %{with ppc64opt2}
+%global optflags %(echo %{optflags} | sed 's/-O2 /-O1 /')
+%endif
+%endif
 
 Name:           gambit-c
 Version:        4.6.5
-Release:        1%{?dist}
+Release:        2%{?dist}
 Summary:        Scheme programming system
 
 Group:          Development/Languages
@@ -16,11 +24,6 @@ Source0:        http://www.iro.umontreal.ca/~gambit/download/gambit/v4.6/source/
 Source1:        gambit-init.el
 Patch0:         gambc-v4_2_8-modtime.patch
 
-# https://bugzilla.redhat.com/show_bug.cgi?id=808285
-%if ! %{with ppc64}
-ExcludeArch:	ppc64
-%endif
-
 BuildRequires:  emacs
 Requires:       gcc
 
@@ -173,6 +176,9 @@ fi
 
 
 %changelog
+* Sat Mar 31 2012 Michel Salim <salimma@fedoraproject.org> - 4.6.5-2
+- Reduce optimization level on ppc64 to work around gcc compilation error
+
 * Thu Mar 29 2012 Michel Salim <salimma@fedoraproject.org> - 4.6.5-1
 - Update to 4.6.5
 - Drop termite subpackages, they have been disabled for many releases