diff --git a/lua/colorbuddy/data/rgb.lua b/lua/colorbuddy/data/rgb.lua
index e36afae..96bf55a 100644
--- a/lua/colorbuddy/data/rgb.lua
+++ b/lua/colorbuddy/data/rgb.lua
@@ -26,7 +26,7 @@ end
 
 function RGB:from_string(str)
   assert(str:sub(1, 1) == "#", "string color: improperly formatted #RRGGBB")
-  assert(str:len() == 7, "string color: improper length, must be 7")
+  assert(str:len() == 7, "string color: improper length, must be len( \"#RRGGBB\" ) == 7")
 
   return RGB:new(
     tonumber(str:sub(2, 3), 16) / 255,