diff --git a/qrexec-lib/qrexec.h b/qrexec-lib/qrexec.h
index 5d4ce81..43ee088 100644
--- a/qrexec-lib/qrexec.h
+++ b/qrexec-lib/qrexec.h
@@ -28,6 +28,9 @@
 #define MAX_DATA_CHUNK 4096
 
 #define RPC_REQUEST_COMMAND "QUBESRPC"
+#define RPC_REQUEST_COMMAND_LEN (sizeof(RPC_REQUEST_COMMAND)-1)
+#define NOGUI_CMD_PREFIX "nogui:"
+#define NOGUI_CMD_PREFIX_LEN (sizeof(NOGUI_CMD_PREFIX)-1)
 #define VCHAN_BASE_PORT 512
 #define MAX_DATA_CHUNK 4096