diff --git a/lib/veksel/suffix.rb b/lib/veksel/suffix.rb
index 0ec0f16..d7e4b7b 100644
--- a/lib/veksel/suffix.rb
+++ b/lib/veksel/suffix.rb
@@ -3,7 +3,7 @@ class Suffix
     PROTECTED_BRANCHES = %w[master main].freeze
 
     def initialize(branch_name)
-      @branch_name = branch_name
+      @branch_name = String(branch_name)
     end
 
     def to_s