diff --git a/ChangeLog b/ChangeLog
index d15b6a8..5000302 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2018-05-01  John Ericson  <john.ericson@obsidian.systems>
+
+	* config.sub: Rewrite basic_machine 'if' with 'case'.
+
 2018-05-01  Francois H. Theron  <francois.theron@netronome.com>
 	    Ben Elliston  <bje@gnu.org>
 
diff --git a/config.sub b/config.sub
index 36c4ad6..897694f 100755
--- a/config.sub
+++ b/config.sub
@@ -128,9 +128,14 @@ case $maybe_os in
     ;;
   *)
     basic_machine=`echo "$1" | sed 's/-[^-]*$//'`
-    if [ "$basic_machine" != "$1" ]
-    then os=`echo "$1" | sed 's/.*-/-/'`
-    else os=; fi
+    case $1 in
+      *-*)
+	  os=`echo "$1" | sed 's/.*-/-/'`
+	  ;;
+      *)
+	  os=
+	  ;;
+    esac
     ;;
 esac