diff --git a/ethcore/sync/src/block_sync.rs b/ethcore/sync/src/block_sync.rs
index 7eb324a06..cc3755c9d 100644
--- a/ethcore/sync/src/block_sync.rs
+++ b/ethcore/sync/src/block_sync.rs
@@ -571,6 +571,8 @@ impl BlockDownloader {
 				},
 				Err(EthcoreError::Import(ImportError::AlreadyQueued)) => {
 					trace_sync!(self, "Block already queued {:?}", h);
+					// Treat blocks in queue as imported in order not to start retraction too early
+					imported.insert(h.clone());
 					self.block_imported(&h, number, &parent);
 				},
 				Ok(_) => {