diff --git a/lib/solargraph/source/fragment.rb b/lib/solargraph/source/fragment.rb
index 31ebf4b69..4b2ee0cb7 100644
--- a/lib/solargraph/source/fragment.rb
+++ b/lib/solargraph/source/fragment.rb
@@ -155,7 +155,7 @@ def remainder
       #
       # @return [String]
       def whole_word
-        @whole_word ||= word + remainder
+        @whole_word ||= word + remainder.to_s
       end
 
       # Get the whole signature at the current offset, including the final