diff --git a/ChangeLog b/ChangeLog
index 7e77e93..43d4550 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2009-09-18  Jack Howarth  <howarth@bromo.med.uc.edu>
+
+	* config.guess (*:Darwin:*:*): Handle 64-bit compilers on i386.
+
 2009-09-18  Ben Elliston  <bje@gnu.org>
 
 	* config.guess (i*86:Linux:*:*): Remove checks for whether the
diff --git a/config.guess b/config.guess
index 0e902ee..e792aac 100755
--- a/config.guess
+++ b/config.guess
@@ -1198,6 +1198,16 @@ EOF
     *:Darwin:*:*)
 	UNAME_PROCESSOR=`uname -p` || UNAME_PROCESSOR=unknown
 	case $UNAME_PROCESSOR in
+	    i386)
+		eval $set_cc_for_build
+		if [ "$CC_FOR_BUILD" != 'no_compiler_found' ]; then
+		  if (echo '#ifdef __LP64__'; echo IS_64BIT_ARCH; echo '#endif') | \
+		      (CCOPTS= $CC_FOR_BUILD -E - 2>/dev/null) | \
+		      grep IS_64BIT_ARCH >/dev/null
+		  then
+		      UNAME_PROCESSOR="x86_64"
+		  fi
+		fi ;;
 	    unknown) UNAME_PROCESSOR=powerpc ;;
 	esac
 	echo ${UNAME_PROCESSOR}-apple-darwin${UNAME_RELEASE}