diff --git a/libports/src/server/ffat_fs/main.cc b/libports/src/server/ffat_fs/main.cc
index 0b7d6ad2d..b6de6ca91 100644
--- a/libports/src/server/ffat_fs/main.cc
+++ b/libports/src/server/ffat_fs/main.cc
@@ -852,6 +852,9 @@ namespace File_system {
 			{
 				PWRN("File_system::Session::sigh not supported");
 			}
+
+			/* ffat only supports fsync(2) */
+			void sync() { }
 	};
 
 
diff --git a/os/src/server/lx_fs/main.cc b/os/src/server/lx_fs/main.cc
index 6096286c1..16d827256 100644
--- a/os/src/server/lx_fs/main.cc
+++ b/os/src/server/lx_fs/main.cc
@@ -308,6 +308,13 @@ class File_system::Session_component : public Session_rpc_object
 		{
 			_handle_registry.sigh(node_handle, sigh);
 		}
+
+		/**
+		 * We could call sync(2) here but for now we forward just the
+		 * reminder because besides testing, there is currently no
+		 * use-case.
+		 */
+		void sync() { PWRN("sync() not implemented!"); }
 };
 
 
diff --git a/os/src/server/ram_fs/main.cc b/os/src/server/ram_fs/main.cc
index def037c16..63a967a76 100644
--- a/os/src/server/ram_fs/main.cc
+++ b/os/src/server/ram_fs/main.cc
@@ -411,6 +411,8 @@ namespace File_system {
 			{
 				_handle_registry.sigh(node_handle, sigh);
 			}
+
+			void sync() { }
 	};
 
 
diff --git a/os/src/server/tar_fs/main.cc b/os/src/server/tar_fs/main.cc
index aeb2ad58d..900b67685 100644
--- a/os/src/server/tar_fs/main.cc
+++ b/os/src/server/tar_fs/main.cc
@@ -424,6 +424,9 @@ namespace File_system {
 			{
 				PWRN("File_system::Session::sigh not supported");
 			}
+
+			/* merely readonly, no need to sync */
+			void sync() { }
 	};