diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index 8d9407c..14ac65e 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -292,7 +292,7 @@
  * \return          0 if context can't do the operations,
  *                  1 otherwise.
  */
-int pk_can_do( pk_context *ctx, pk_type_t type );
+int pk_can_do( const pk_context *ctx, pk_type_t type );
 
 /**
  * \brief           Verify signature (including padding if relevant).