diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index 2d08071948..40ee78f90f 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -81,6 +81,7 @@ var (
 	errTimeout                 = errors.New("timeout")
 	errEmptyHeaderSet          = errors.New("empty header set by peer")
 	errPeersUnavailable        = errors.New("no peers available or all tried for download")
+	errNoAncestor              = errors.New("no common ancestor")
 	errInvalidAncestor         = errors.New("retrieved ancestor is invalid")
 	errInvalidChain            = errors.New("retrieved hash chain is invalid")
 	errInvalidBody             = errors.New("retrieved block body is invalid")
@@ -711,8 +712,10 @@ func (d *Downloader) findAncestor(p *peerConnection, remoteHeader *types.Header)
 		localHeight = d.blockchain.CurrentBlock().NumberU64()
 	case FastSync:
 		localHeight = d.blockchain.CurrentFastBlock().NumberU64()
-	default:
+	case LightSync:
 		localHeight = d.lightchain.CurrentHeader().Number.Uint64()
+	default:
+		log.Crit("unknown sync mode", "mode", d.mode)
 	}
 	p.log.Debug("Looking for common ancestor", "local", localHeight, "remote", remoteHeight)
 
@@ -741,9 +744,36 @@ func (d *Downloader) findAncestor(p *peerConnection, remoteHeader *types.Header)
 		}
 	}
 
+	// Only attempt span search if local head is "close" to reported remote
+	if remoteHeight-localHeight < uint64(MaxHeaderFetch) {
+		a, err := d.findAncestorSpanSearch(p, remoteHeight, localHeight, floor)
+		if err == nil {
+			if a > localHeight {
+				a = localHeight
+			}
+			return a, nil
+		} else if err != errNoAncestor {
+			return 0, err
+		}
+	}
+
+	// Ancestor not found, we need to binary search over our chain
+	a, err := d.findAncestorBinarySearch(p, remoteHeight, floor)
+	if err != nil {
+		return 0, err
+	}
+	if a > localHeight {
+		a = localHeight
+	}
+	return a, nil
+}
+
+// findAncestorSpanSearch looks for a common ancestor by requesting a spaced set of headers between ours and theirs.
+func (d *Downloader) findAncestorSpanSearch(p *peerConnection, remoteHeight, localHeight uint64, floor int64) (uint64, error) {
 	from, count, skip, max := calculateRequestSpan(remoteHeight, localHeight)
 
 	p.log.Trace("Span searching for common ancestor", "count", count, "from", from, "skip", skip)
+
 	go p.peer.RequestHeadersByNumber(uint64(from), count, skip, false)
 
 	// Wait for the remote response to the head fetch
@@ -794,8 +824,10 @@ func (d *Downloader) findAncestor(p *peerConnection, remoteHeader *types.Header)
 					known = d.blockchain.HasBlock(h, n)
 				case FastSync:
 					known = d.blockchain.HasFastBlock(h, n)
-				default:
+				case LightSync:
 					known = d.lightchain.HasHeader(h, n)
+				default:
+					log.Crit("unknown sync mode", "mode", d.mode)
 				}
 				if known {
 					number, hash = n, h
@@ -821,13 +853,19 @@ func (d *Downloader) findAncestor(p *peerConnection, remoteHeader *types.Header)
 		p.log.Debug("Found common ancestor", "number", number, "hash", hash)
 		return number, nil
 	}
-	// Ancestor not found, we need to binary search over our chain
+	return 0, errNoAncestor
+}
+
+// findAncestorBinarySearch negotiates a binary search using their reported chain.
+func (d *Downloader) findAncestorBinarySearch(p *peerConnection, remoteHeight uint64, floor int64) (uint64, error) {
 	start, end := uint64(0), remoteHeight
 	if floor > 0 {
 		start = uint64(floor)
 	}
 	p.log.Trace("Binary searching for common ancestor", "start", start, "end", end)
 
+	// Wait for the remote response to the head fetch
+	hash := common.Hash{}
 	for start+1 < end {
 		// Split our chain interval in two, and request the hash to cross check
 		check := (start + end) / 2
@@ -867,8 +905,10 @@ func (d *Downloader) findAncestor(p *peerConnection, remoteHeader *types.Header)
 					known = d.blockchain.HasBlock(h, n)
 				case FastSync:
 					known = d.blockchain.HasFastBlock(h, n)
-				default:
+				case LightSync:
 					known = d.lightchain.HasHeader(h, n)
+				default:
+					log.Crit("unknown sync mode", "mode", d.mode)
 				}
 				if !known {
 					end = check