diff --git a/gl/build-aux/options-parser b/gl/build-aux/options-parser
index fbcbf1ba..af460fd1 100644
--- a/gl/build-aux/options-parser
+++ b/gl/build-aux/options-parser
@@ -499,7 +499,7 @@ else
   {
       $debug_cmd
 
-      func_split_equals_lhs=`expr "x$1" : 'x\([^=]*)'`
+      func_split_equals_lhs=`expr "x$1" : 'x\([^=]*\)'`
       func_split_equals_rhs=
       test "x$func_split_equals_lhs" = "x$1" \
         || func_split_equals_rhs=`expr "x$1" : 'x[^=]*=\(.*\)$'`