diff --git a/src/tbf.cpp b/src/tbf.cpp
index 7ebd268..153ba80 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -96,7 +96,7 @@
 	trx(NULL),
 	first_ts(0),
 	first_common_ts(0),
-	control_ts(0xff),
+	control_ts(TBF_CONTROL_TS_UNSET),
 	fT(0),
 	num_fT_exp(0),
 	upgrade_to_multislot(false),
@@ -328,7 +328,7 @@
 
 int tbf_assign_control_ts(struct gprs_rlcmac_tbf *tbf)
 {
-	if (tbf->control_ts == 0xff)
+	if (tbf->control_ts == TBF_CONTROL_TS_UNSET)
 		LOGPTBF(tbf, LOGL_INFO, "Setting Control TS %d\n",
 			tbf->first_common_ts);
 	else if (tbf->control_ts != tbf->first_common_ts)
diff --git a/src/tbf.h b/src/tbf.h
index 3aaf9fb..05beed5 100644
--- a/src/tbf.h
+++ b/src/tbf.h
@@ -116,6 +116,8 @@
 #define GPRS_RLCMAC_FLAG_TO_DL_ACK	3 /* DL TBF: Failed to receive last polled DL ACK/NACK */
 #define GPRS_RLCMAC_FLAG_TO_MASK	0xf0 /* timeout bits */
 
+#define TBF_CONTROL_TS_UNSET 0xff
+
 #define T_START(tbf, t, T, r, f) tbf->t_start(t, T, r, f, __FILE__, __LINE__)
 
 #ifdef __cplusplus