diff --git a/eth/fetcher/fetcher_test.go b/eth/fetcher/fetcher_test.go
index 00fad3498..4c6a1bf6a 100644
--- a/eth/fetcher/fetcher_test.go
+++ b/eth/fetcher/fetcher_test.go
@@ -4,6 +4,7 @@ import (
 	"encoding/binary"
 	"errors"
 	"math/big"
+	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
@@ -67,15 +68,17 @@ func createBlocksFromHashes(hashes []common.Hash) map[common.Hash]*types.Block {
 type fetcherTester struct {
 	fetcher *Fetcher
 
-	ownHashes []common.Hash                // Hash chain belonging to the tester
-	ownBlocks map[common.Hash]*types.Block // Blocks belonging to the tester
+	hashes []common.Hash                // Hash chain belonging to the tester
+	blocks map[common.Hash]*types.Block // Blocks belonging to the tester
+
+	lock sync.RWMutex
 }
 
 // newTester creates a new fetcher test mocker.
 func newTester() *fetcherTester {
 	tester := &fetcherTester{
-		ownHashes: []common.Hash{knownHash},
-		ownBlocks: map[common.Hash]*types.Block{knownHash: genesis},
+		hashes: []common.Hash{knownHash},
+		blocks: map[common.Hash]*types.Block{knownHash: genesis},
 	}
 	tester.fetcher = New(tester.hasBlock, tester.importBlock, tester.chainHeight)
 	tester.fetcher.Start()
@@ -85,29 +88,38 @@ func newTester() *fetcherTester {
 
 // hasBlock checks if a block is pres	ent in the testers canonical chain.
 func (f *fetcherTester) hasBlock(hash common.Hash) bool {
-	_, ok := f.ownBlocks[hash]
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+
+	_, ok := f.blocks[hash]
 	return ok
 }
 
 // importBlock injects a new blocks into the simulated chain.
 func (f *fetcherTester) importBlock(peer string, block *types.Block) error {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+
 	// Make sure the parent in known
-	if _, ok := f.ownBlocks[block.ParentHash()]; !ok {
+	if _, ok := f.blocks[block.ParentHash()]; !ok {
 		return errors.New("unknown parent")
 	}
 	// Discard any new blocks if the same height already exists
-	if block.NumberU64() <= f.ownBlocks[f.ownHashes[len(f.ownHashes)-1]].NumberU64() {
+	if block.NumberU64() <= f.blocks[f.hashes[len(f.hashes)-1]].NumberU64() {
 		return nil
 	}
 	// Otherwise build our current chain
-	f.ownHashes = append(f.ownHashes, block.Hash())
-	f.ownBlocks[block.Hash()] = block
+	f.hashes = append(f.hashes, block.Hash())
+	f.blocks[block.Hash()] = block
 	return nil
 }
 
 // chainHeight retrieves the current height (block number) of the chain.
 func (f *fetcherTester) chainHeight() uint64 {
-	return f.ownBlocks[f.ownHashes[len(f.ownHashes)-1]].NumberU64()
+	f.lock.RLock()
+	defer f.lock.RUnlock()
+
+	return f.blocks[f.hashes[len(f.hashes)-1]].NumberU64()
 }
 
 // peerFetcher retrieves a fetcher associated with a simulated peer.
@@ -149,7 +161,7 @@ func TestSequentialAnnouncements(t *testing.T) {
 		tester.fetcher.Notify("valid", hashes[i], time.Now().Add(-arriveTimeout), fetcher)
 		time.Sleep(50 * time.Millisecond)
 	}
-	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
+	if imported := len(tester.blocks); imported != targetBlocks+1 {
 		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
 	}
 }
@@ -179,7 +191,7 @@ func TestConcurrentAnnouncements(t *testing.T) {
 
 		time.Sleep(50 * time.Millisecond)
 	}
-	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
+	if imported := len(tester.blocks); imported != targetBlocks+1 {
 		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
 	}
 	// Make sure no blocks were retrieved twice
@@ -207,7 +219,7 @@ func TestOverlappingAnnouncements(t *testing.T) {
 	}
 	time.Sleep(overlap * delay)
 
-	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
+	if imported := len(tester.blocks); imported != targetBlocks+1 {
 		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
 	}
 }
@@ -242,7 +254,7 @@ func TestPendingDeduplication(t *testing.T) {
 	time.Sleep(delay)
 
 	// Check that all blocks were imported and none fetched twice
-	if imported := len(tester.ownBlocks); imported != 2 {
+	if imported := len(tester.blocks); imported != 2 {
 		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, 2)
 	}
 	if int(counter) != 1 {
@@ -273,7 +285,7 @@ func TestRandomArrivalImport(t *testing.T) {
 	tester.fetcher.Notify("valid", hashes[skip], time.Now().Add(-arriveTimeout), fetcher)
 	time.Sleep(50 * time.Millisecond)
 
-	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
+	if imported := len(tester.blocks); imported != targetBlocks+1 {
 		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
 	}
 }
@@ -301,7 +313,7 @@ func TestQueueGapFill(t *testing.T) {
 	tester.fetcher.Enqueue("valid", blocks[hashes[skip]])
 	time.Sleep(50 * time.Millisecond)
 
-	if imported := len(tester.ownBlocks); imported != targetBlocks+1 {
+	if imported := len(tester.blocks); imported != targetBlocks+1 {
 		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, targetBlocks+1)
 	}
 }
@@ -334,7 +346,7 @@ func TestImportDeduplication(t *testing.T) {
 	tester.fetcher.Enqueue("valid", blocks[hashes[1]])
 	time.Sleep(50 * time.Millisecond)
 
-	if imported := len(tester.ownBlocks); imported != 3 {
+	if imported := len(tester.blocks); imported != 3 {
 		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, 3)
 	}
 	if counter != 2 {
@@ -353,8 +365,8 @@ func TestDistantDiscarding(t *testing.T) {
 
 	// Create a tester and simulate a head block being the middle of the above chain
 	tester := newTester()
-	tester.ownHashes = []common.Hash{head}
-	tester.ownBlocks = map[common.Hash]*types.Block{head: blocks[head]}
+	tester.hashes = []common.Hash{head}
+	tester.blocks = map[common.Hash]*types.Block{head: blocks[head]}
 
 	// Ensure that a block with a lower number than the threshold is discarded
 	tester.fetcher.Enqueue("lower", blocks[hashes[0]])
@@ -413,10 +425,10 @@ func TestCompetingImports(t *testing.T) {
 	tester.fetcher.Enqueue("chain C", blocksC[hashesC[len(hashesC)-2]])
 
 	start := time.Now()
-	for len(tester.ownHashes) != len(hashesA) && time.Since(start) < time.Second {
+	for len(tester.hashes) != len(hashesA) && time.Since(start) < time.Second {
 		time.Sleep(50 * time.Millisecond)
 	}
-	if len(tester.ownHashes) != len(hashesA) {
-		t.Fatalf("chain length mismatch: have %v, want %v", len(tester.ownHashes), len(hashesA))
+	if len(tester.hashes) != len(hashesA) {
+		t.Fatalf("chain length mismatch: have %v, want %v", len(tester.hashes), len(hashesA))
 	}
 }