diff --git a/src/mapcss/StyleChooser.py b/src/mapcss/StyleChooser.py
index 09b8f97..41192d8 100644
--- a/src/mapcss/StyleChooser.py
+++ b/src/mapcss/StyleChooser.py
@@ -135,7 +135,8 @@ class StyleChooser:
                         "hack to support josm's style casings"
                         if b.strip()[0] = "+":
                           try:
-                            ra[a] = float(b) / 2.
+                            b = float(b) / 2.
+                            ra[a] = b
                           except ValueError:
                             pass