diff --git a/src/frontend/numparam/mystring.c b/src/frontend/numparam/mystring.c
index d699522f6..8918de630 100644
--- a/src/frontend/numparam/mystring.c
+++ b/src/frontend/numparam/mystring.c
@@ -142,7 +142,7 @@ alfa(char c)
     return
         ((c >= 'a') && (c <= 'z')) ||
         ((c >= 'A') && (c <= 'Z')) ||
-        c == '_' || c == '[' || c == ']';
+        c == '_' || c == '[' || c == ']' || ((c) & 0200);
 }