diff --git a/radio/processor/src/Block.hpp b/radio/processor/src/Block.hpp
index b687c63..76a1528 100644
--- a/radio/processor/src/Block.hpp
+++ b/radio/processor/src/Block.hpp
@@ -24,22 +24,22 @@ class Block
 	
 	virtual void process() = 0;
 
-	IBuffer* buffer_in(size_t index=0)
+	IBuffer* buffer_in(size_t index=0) const
 	{
 		return m_buf_in;
 	}
 
-	IBuffer* buffer_out(size_t index=0)
+	IBuffer* buffer_out(size_t index=0) const
 	{
 		return m_buf_out;
 	}
 
-	size_t num_in()
+	size_t num_in() const
 	{
 		return m_num_in;
 	}
 
-	size_t num_out()
+	size_t num_out() const
 	{
   		return m_num_out;
 	}