diff --git a/ChangeLog b/ChangeLog
index cc880a4..7295df3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2018-05-05  Ben Elliston  <bje@gnu.org>
+
+	* config.sub: Simplify an if expression.
+
 2018-05-05  John Ericson  <john.ericson@obsidian.systems>
 
 	* config.sub (arm*-*-none-eabi): Recognise.
diff --git a/config.sub b/config.sub
index 2456377..20f7cf2 100755
--- a/config.sub
+++ b/config.sub
@@ -1360,7 +1360,7 @@ esac
 
 # Decode manufacturer-specific aliases for certain operating systems.
 
-if [ x"$os" != x"" ]
+if [ x$os != x ]
 then
 case $os in
 	# First match some system type aliases that might get confused