diff --git a/libi2pd_client/I2CP.cpp b/libi2pd_client/I2CP.cpp
index f6494a51..df93082b 100644
--- a/libi2pd_client/I2CP.cpp
+++ b/libi2pd_client/I2CP.cpp
@@ -571,7 +571,7 @@ namespace client
 			m_IsSending = false;
 	}
 
-	std::string_view I2CPSession::ExtractString (const uint8_t * buf, size_t len)
+	std::string_view I2CPSession::ExtractString (const uint8_t * buf, size_t len) const
 	{
 		uint8_t l = buf[0];
 		if (l > len) l = len;
@@ -588,7 +588,7 @@ namespace client
 		return l + 1;
 	}
 
-	void I2CPSession::ExtractMapping (const uint8_t * buf, size_t len, std::map<std::string, std::string>& mapping)
+	void I2CPSession::ExtractMapping (const uint8_t * buf, size_t len, std::map<std::string, std::string>& mapping) const
 	// TODO: move to Base.cpp
 	{
 		size_t offset = 0;
diff --git a/libi2pd_client/I2CP.h b/libi2pd_client/I2CP.h
index 50b668d3..d3949eaa 100644
--- a/libi2pd_client/I2CP.h
+++ b/libi2pd_client/I2CP.h
@@ -194,9 +194,9 @@ namespace client
 
 			void HandleI2CPMessageSent (const boost::system::error_code& ecode, std::size_t bytes_transferred);
 
-			std::string_view ExtractString (const uint8_t * buf, size_t len);
+			std::string_view ExtractString (const uint8_t * buf, size_t len) const;
 			size_t PutString (uint8_t * buf, size_t len, std::string_view str);
-			void ExtractMapping (const uint8_t * buf, size_t len, std::map<std::string, std::string>& mapping);
+			void ExtractMapping (const uint8_t * buf, size_t len, std::map<std::string, std::string>& mapping) const;
 			void SendSessionStatusMessage (I2CPSessionStatus status);
 			void SendHostReplyMessage (uint32_t requestID, std::shared_ptr<const i2p::data::IdentityEx> identity);