diff --git a/client_http.hpp b/client_http.hpp
index e12fcd2..87d8367 100644
--- a/client_http.hpp
+++ b/client_http.hpp
@@ -72,11 +72,11 @@ namespace SimpleWeb {
       friend class ClientBase<socket_type>;
 
     public:
-      std::size_t size() noexcept {
+      std::size_t size() const noexcept {
         return streambuf.size();
       }
       /// Convenience function to return content as a string.
-      std::string string() noexcept {
+      std::string string() const noexcept {
         return std::string(asio::buffers_begin(streambuf.data()), asio::buffers_end(streambuf.data()));
       }
 
diff --git a/server_http.hpp b/server_http.hpp
index b7591c2..baace86 100644
--- a/server_http.hpp
+++ b/server_http.hpp
@@ -135,7 +135,7 @@ namespace SimpleWeb {
       }
 
     public:
-      std::size_t size() noexcept {
+      std::size_t size() const noexcept {
         return streambuf->size();
       }
 
@@ -209,11 +209,11 @@ namespace SimpleWeb {
       friend class ServerBase<socket_type>;
 
     public:
-      std::size_t size() noexcept {
+      std::size_t size() const noexcept {
         return streambuf.size();
       }
       /// Convenience function to return content as std::string.
-      std::string string() noexcept {
+      std::string string() const noexcept {
         return std::string(asio::buffers_begin(streambuf.data()), asio::buffers_end(streambuf.data()));
       }