diff --git a/lib/geocoder.rb b/lib/geocoder.rb
index 8aec8c33ca3a7c257c0cd352b68b6a0e63956e92..53e7133ae062fce5ebcde885306a97fd007702a2 100644
--- a/lib/geocoder.rb
+++ b/lib/geocoder.rb
@@ -78,6 +78,9 @@ module Geocoder
   ##
   # Does the given value look like an IP address?
   #
+  # Does not check for actual validity, just the appearance of four
+  # dot-delimited 8-bit numbers.
+  #
   def ip_address?(value)
     value.match /^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/
   end