diff --git a/ntp_core.c b/ntp_core.c
index 55f1e96..53858f6 100644
--- a/ntp_core.c
+++ b/ntp_core.c
@@ -891,6 +891,10 @@ transmit_timeout(void *arg)
 
   switch (inst->opmode) {
     case MD_BURST_WAS_ONLINE:
+      /* When not reachable, don't stop online burst until sending succeeds */
+      if (!sent && !SRC_IsReachable(inst->source))
+        break;
+      /* Fall through */
     case MD_BURST_WAS_OFFLINE:
       --inst->burst_total_samples_to_go;
       break;
diff --git a/sources.c b/sources.c
index b9e095d..e24463d 100644
--- a/sources.c
+++ b/sources.c
@@ -1167,6 +1167,14 @@ SRC_IsSyncPeer(SRC_Instance inst)
 
 /* ================================================== */
 
+int
+SRC_IsReachable(SRC_Instance inst)
+{
+  return inst->reachability != 0;
+}
+
+/* ================================================== */
+
 int
 SRC_ReadNumberOfSources(void)
 {
diff --git a/sources.h b/sources.h
index 64c450d..c28102c 100644
--- a/sources.h
+++ b/sources.h
@@ -171,6 +171,7 @@ extern void SRC_DumpSources(void);
 extern void SRC_ReloadSources(void);
 
 extern int SRC_IsSyncPeer(SRC_Instance inst);
+extern int SRC_IsReachable(SRC_Instance inst);
 extern int SRC_ReadNumberOfSources(void);
 extern int SRC_ActiveSources(void);
 extern int SRC_ReportSource(int index, RPT_SourceReport *report, struct timeval *now);