diff --git a/tx.go b/tx.go
index 869d41200..c9199501d 100644
--- a/tx.go
+++ b/tx.go
@@ -1,6 +1,7 @@
 package bbolt
 
 import (
+	"crypto/sha1"
 	"fmt"
 	"io"
 	"os"
@@ -483,6 +484,20 @@ func (tx *Tx) checkBucket(b *Bucket, reachable map[pgid]*page, freed map[pgid]bo
 		}
 	})
 
+	// Check all the keys in this bucket, and raise an error if there are duplicated keys.
+	cachedKeys := map[[sha1.Size]byte][]byte{}
+	b.ForEach(func(key, _ []byte) error {
+		sha1Key := sha1.Sum(key)
+		if val, ok := cachedKeys[sha1Key]; ok {
+			ch <- fmt.Errorf("duplicated key: %q found", val)
+		} else {
+			cachedKeys[sha1Key] = key
+		}
+		return nil
+	})
+	// clear the map
+	cachedKeys = map[[sha1.Size]byte][]byte{}
+
 	// Check each bucket within this bucket.
 	_ = b.ForEach(func(k, v []byte) error {
 		if child := b.Bucket(k); child != nil {