diff --git a/ntp_sources.c b/ntp_sources.c
index 1257f57..64d9a8b 100644
--- a/ntp_sources.c
+++ b/ntp_sources.c
@@ -1056,7 +1056,10 @@ resolve_source_replacement(SourceRecord *record, int refreshment)
   us->address = *record->remote_addr;
 
   append_unresolved_source(us);
-  NSR_ResolveSources();
+
+  /* Don't restart resolving round if already running */
+  if (!resolving_source)
+    NSR_ResolveSources();
 }
 
 /* ================================================== */