diff --git a/excel-esv.gemspec b/excel-esv.gemspec
index 5c19eef..90e31b0 100644
--- a/excel-esv.gemspec
+++ b/excel-esv.gemspec
@@ -17,4 +17,5 @@ Gem::Specification.new do |spec|
   spec.require_paths = [ "lib" ]
 
   spec.add_dependency "spreadsheet"
+  spec.add_runtime_dependency "logger"
 end