diff --git a/src/connection.c b/src/connection.c
index 45a2e784..bc373f6b 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -314,6 +314,12 @@ wl_connection_flush(struct wl_connection *connection)
 	return connection->out.head - tail;
 }
 
+uint32_t
+wl_connection_pending_input(struct wl_connection *connection)
+{
+	return wl_buffer_size(&connection->in);
+}
+
 int
 wl_connection_read(struct wl_connection *connection)
 {
@@ -350,7 +356,7 @@ wl_connection_read(struct wl_connection *connection)
 
 	connection->in.head += len;
 
-	return connection->in.head - connection->in.tail;
+	return wl_connection_pending_input(connection);
 }
 
 int
diff --git a/src/wayland-private.h b/src/wayland-private.h
index 0e3420c3..da578d16 100644
--- a/src/wayland-private.h
+++ b/src/wayland-private.h
@@ -122,6 +122,9 @@ wl_connection_consume(struct wl_connection *connection, size_t size);
 int
 wl_connection_flush(struct wl_connection *connection);
 
+uint32_t
+wl_connection_pending_input(struct wl_connection *connection);
+
 int
 wl_connection_read(struct wl_connection *connection);
 
diff --git a/src/wayland-server.c b/src/wayland-server.c
index 9e26b185..2158c088 100644
--- a/src/wayland-server.c
+++ b/src/wayland-server.c
@@ -313,7 +313,6 @@ wl_client_connection_data(int fd, uint32_t mask, void *data)
 
 		closure = wl_connection_demarshal(client->connection, size,
 						  &client->objects, message);
-		len -= size;
 
 		if (closure == NULL && errno == ENOMEM) {
 			wl_resource_post_no_memory(resource);
@@ -346,6 +345,8 @@ wl_client_connection_data(int fd, uint32_t mask, void *data)
 
 		if (client->error)
 			break;
+
+		len = wl_connection_pending_input(connection);
 	}
 
 	if (client->error)