diff --git a/lib/pry/code.rb b/lib/pry/code.rb
index c0f1d508..0986ea25 100644
--- a/lib/pry/code.rb
+++ b/lib/pry/code.rb
@@ -110,7 +110,7 @@ class Pry
         lines = lines.lines
       end
 
-      @lines = lines.each_with_index.map { |l, i| [l.chomp, i + start_line] }
+      @lines = lines.each_with_index.map { |l, i| [l.chomp, i + start_line.to_i] }
       @code_type = code_type
     end