diff --git a/mlton.spec b/mlton.spec
index 900a5d2..b9429fa 100644
--- a/mlton.spec
+++ b/mlton.spec
@@ -2,7 +2,7 @@
 
 Name:		mlton
 Version:	20100608
-Release:	3%{?dist}
+Release:	4%{?dist}
 Summary:	Optimizing compiler for Standard ML
 
 Group:		Development/Languages
@@ -20,6 +20,9 @@ BuildRequires:	gmp-devel htmldoc tex(latex)
 BuildRequires:	mlton
 %endif
 
+# bootstrapped only on these architectures
+ExclusiveArch:  %{ix86} x86_64 %{arm} ppc
+
 Requires:	gmp-devel gcc
 
 
@@ -85,6 +88,9 @@ rm -rf $RPM_BUILD_ROOT%{_libdir}/mlton/sml/ckit-lib/regression
 
 
 %changelog
+* Fri Mar 11 2011 Dan Horák <dan[at]danny.cz> - 20100608-4
+- set ExclusiveArch
+
 * Tue Feb 08 2011 Fedora Release Engineering <rel-eng@lists.fedoraproject.org> - 20100608-3
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_15_Mass_Rebuild