diff --git a/consensus/ethash/algorithm.go b/consensus/ethash/algorithm.go
index d6c871092e..2b01f2843e 100644
--- a/consensus/ethash/algorithm.go
+++ b/consensus/ethash/algorithm.go
@@ -18,6 +18,7 @@ package ethash
 
 import (
 	"encoding/binary"
+	"fmt"
 	"hash"
 	"math/big"
 	"reflect"
@@ -374,7 +375,7 @@ func hashimoto(hash []byte, nonce uint64, size uint64, lookup func(index uint32)
 // hashimotoLight aggregates data from the full dataset (using only a small
 // in-memory cache) in order to produce our final value for a particular header
 // hash and nonce.
-func hashimotoLight(size uint64, cache []uint32, hash []byte, nonce uint64) ([]byte, []byte) {
+func hashimotoLight(size uint64, cache []uint32, hash []byte, nonce uint64, verbose bool) ([]byte, []byte) {
 	keccak512 := makeHasher(sha3.NewLegacyKeccak512())
 
 	lookup := func(index uint32) []uint32 {
@@ -384,6 +385,9 @@ func hashimotoLight(size uint64, cache []uint32, hash []byte, nonce uint64) ([]b
 		for i := 0; i < len(data); i++ {
 			data[i] = binary.LittleEndian.Uint32(rawData[i*4:])
 		}
+		if verbose {
+			fmt.Printf("lookup(%d)=%x\n", index, data)
+		}
 		return data
 	}
 	return hashimoto(hash, nonce, size, lookup)
diff --git a/consensus/ethash/consensus.go b/consensus/ethash/consensus.go
index c71001f424..d427f1b353 100644
--- a/consensus/ethash/consensus.go
+++ b/consensus/ethash/consensus.go
@@ -546,17 +546,21 @@ func (ethash *Ethash) verifySeal(chain consensus.ChainReader, header *types.Head
 		ctx = append(ctx, "hdr.nonce", nonce)
 		sealHash := ethash.SealHash(header).Bytes()
 		ctx = append(ctx, "sealHash", fmt.Sprintf("%x", sealHash))
-		digest, result = hashimotoLight(size, cache.cache, sealHash, nonce)
+		verbose := (number == 5901768)
+
+		digest, result = hashimotoLight(size, cache.cache, sealHash, nonce, verbose)
 		ctx = append(ctx, "result", fmt.Sprintf("%x", result))
 		ctx = append(ctx, "epoch", cache.epoch)
 		ctx = append(ctx, "cachedir", ethash.config.CacheDir)
 		ctx = append(ctx, "datasetdir", ethash.config.DatasetDir)
 		// For debuggging only
-		sum := uint32(0)
-		for _, val := range cache.cache {
-			sum = sum ^ val
+		if verbose {
+			sum := uint32(0)
+			for _, val := range cache.cache {
+				sum = sum ^ val
+			}
+			ctx = append(ctx, "cachexor", fmt.Sprintf("%x", sum))
 		}
-		ctx = append(ctx, "cachexor", fmt.Sprintf("%x", sum))
 
 		// Caches are unmapped in a finalizer. Ensure that the cache stays alive
 		// until after the call to hashimotoLight so it's not unmapped while being used.