diff --git a/ChangeLog b/ChangeLog
index f25dbc955..add93301e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2005-04-27  Ben Maurer  <bmaurer@ximian.com>
+
+	* configure.in: amd64 build fix
+
 2005-04-26  Miguel de Icaza  <miguel@novell.com>
 
 	* gtkdotnet/Graphics.cs: Contribution from Sebastian Faltoni
diff --git a/configure.in b/configure.in
index f3e4a51d3..fa0d4b567 100644
--- a/configure.in
+++ b/configure.in
@@ -72,7 +72,7 @@ MONO_REQUIRED_VERSION=1.0
 PKG_CHECK_MODULES(MONO_DEPENDENCY, mono >= $MONO_REQUIRED_VERSION, has_mono=true, has_mono=false)
 
 if test "x$has_mono" = "xtrue"; then
-GACUTIL_FLAGS='/package $(PACKAGE_VERSION) /gacdir $(DESTDIR)$(libdir)'
+GACUTIL_FLAGS='/package $(PACKAGE_VERSION) /gacdir $(DESTDIR)$(prefix)/lib'
 GENERATED_SOURCES=generated/*.cs
 AC_PATH_PROG(RUNTIME, mono, no)
 AC_PATH_PROG(CSC, mcs, no)