diff --git a/environment_driver.lua b/environment_driver.lua
index dd9f3fd..733063e 100644
--- a/environment_driver.lua
+++ b/environment_driver.lua
@@ -2,7 +2,7 @@
 local function getValue(env)
     local value = env.getRadiation()
     print(value.radiation, value.unit)
-    local stringValue = toString(value.radiation) .. toString(value.unit)
+    local stringValue = tostring(value.radiation) .. tostring(value.unit)
     return stringValue
 end