diff --git a/src/decrypt-key.hpp b/src/decrypt-key.hpp
index fdccea7..df45428 100644
--- a/src/decrypt-key.hpp
+++ b/src/decrypt-key.hpp
@@ -47,7 +47,7 @@
   }
 
   const Buffer&
-  getKeyBits()
+  getKeyBits() const
   {
     return m_keyBits;
   }