diff --git a/plugins/rechner.lua b/plugins/rechner.lua
index 6074e84..65b9b81 100644
--- a/plugins/rechner.lua
+++ b/plugins/rechner.lua
@@ -1,7 +1,7 @@
 -- Function reference: http://mathjs.org/docs/reference/functions/categorical.html
 
 local function mathjs(exp)
-  local exp = string.gsub(exp, "%,", "%.")
+  local exp = string.gsub(exp, ",", ".")
   local url = 'http://api.mathjs.org/v1/'
   url = url..'?expr='..URL.escape(exp)
   local b,c = http.request(url)