diff --git a/dgraph/cmd/bulk/mapper.go b/dgraph/cmd/bulk/mapper.go
index 8bfbdfb5422..5f500ca1bfa 100644
--- a/dgraph/cmd/bulk/mapper.go
+++ b/dgraph/cmd/bulk/mapper.go
@@ -231,10 +231,16 @@ func (m *mapper) addMapEntry(key []byte, p *pb.Posting, shard int) {
 
 func (m *mapper) processNQuad(nq gql.NQuad) {
 	sid := m.uid(nq.GetSubject())
+	if sid == 0 {
+		panic(fmt.Sprintf("invalid UID with value 0 for %v", nq.GetSubject()))
+	}
 	var oid uint64
 	var de *pb.DirectedEdge
 	if nq.GetObjectValue() == nil {
 		oid = m.uid(nq.GetObjectId())
+		if oid == 0 {
+			panic(fmt.Sprintf("invalid UID with value 0 for %v", nq.GetObjectId()))
+		}
 		de = nq.CreateUidEdge(sid, oid)
 	} else {
 		var err error
diff --git a/gql/mutation.go b/gql/mutation.go
index a96b053af9d..c02c0258efe 100644
--- a/gql/mutation.go
+++ b/gql/mutation.go
@@ -27,7 +27,7 @@ import (
 )
 
 var (
-	errInvalidUID = errors.New("UID has to be greater than one")
+	errInvalidUID = errors.New("UID must to be greater than 0")
 )
 
 // Mutation stores the strings corresponding to set and delete operations.
diff --git a/posting/index.go b/posting/index.go
index 06402596340..022ce2bd11d 100644
--- a/posting/index.go
+++ b/posting/index.go
@@ -91,7 +91,9 @@ func (txn *Txn) addIndexMutations(ctx context.Context, info *indexMutationInfo)
 
 	attr := info.edge.Attr
 	uid := info.edge.Entity
-	x.AssertTrue(uid != 0)
+	if uid == 0 {
+		return errors.New("invalid UID with value 0")
+	}
 	tokens, err := indexTokens(ctx, info)
 	if err != nil {
 		// This data is not indexable
diff --git a/worker/backup_processor.go b/worker/backup_processor.go
index 2043fff349b..74bc842ea21 100644
--- a/worker/backup_processor.go
+++ b/worker/backup_processor.go
@@ -141,6 +141,7 @@ func (pr *BackupProcessor) WriteBackup(ctx context.Context) (*pb.Status, error)
 	stream.ChooseKey = func(item *badger.Item) bool {
 		parsedKey, err := x.Parse(item.Key())
 		if err != nil {
+			glog.Errorf("error %v while parsing key %v during backup. Skip.", err, hex.EncodeToString(item.Key()))
 			return false
 		}
 
diff --git a/worker/draft.go b/worker/draft.go
index 0d52f0e761f..dcfa130a2ba 100644
--- a/worker/draft.go
+++ b/worker/draft.go
@@ -19,6 +19,7 @@ package worker
 import (
 	"bytes"
 	"context"
+	"encoding/hex"
 	"fmt"
 	"sort"
 	"sync"
@@ -240,6 +241,7 @@ func detectPendingTxns(attr string) error {
 	tctxs := posting.Oracle().IterateTxns(func(key []byte) bool {
 		pk, err := x.Parse(key)
 		if err != nil {
+			glog.Errorf("error %v while parsing key %v", err, hex.EncodeToString(key))
 			return false
 		}
 		return pk.Attr == attr
diff --git a/worker/export.go b/worker/export.go
index 4d5632a9f67..e09af4a4892 100644
--- a/worker/export.go
+++ b/worker/export.go
@@ -21,6 +21,7 @@ import (
 	"bytes"
 	"compress/gzip"
 	"context"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"os"
@@ -439,6 +440,7 @@ func export(ctx context.Context, in *pb.ExportRequest) error {
 	stream.ChooseKey = func(item *badger.Item) bool {
 		pk, err := x.Parse(item.Key())
 		if err != nil {
+			glog.Errorf("error %v while parsing key %v during export. Skip.", err, hex.EncodeToString(item.Key()))
 			return false
 		}
 
@@ -469,6 +471,7 @@ func export(ctx context.Context, in *pb.ExportRequest) error {
 		item := itr.Item()
 		pk, err := x.Parse(item.Key())
 		if err != nil {
+			glog.Errorf("error %v while parsing key %v during export. Skip.", err, hex.EncodeToString(item.Key()))
 			return nil, err
 		}
 		e := &exporter{
diff --git a/x/keys.go b/x/keys.go
index 023808e41fc..ce39777eea2 100644
--- a/x/keys.go
+++ b/x/keys.go
@@ -439,7 +439,7 @@ func Parse(key []byte) (ParsedKey, error) {
 	var p ParsedKey
 
 	if len(key) == 0 {
-		return p, errors.Errorf("0 length key")
+		return p, errors.New("0 length key")
 	}
 
 	p.bytePrefix = key[0]
@@ -476,7 +476,9 @@ func Parse(key []byte) (ParsedKey, error) {
 			return p, errors.Errorf("uid length < 8 for key: %q, parsed key: %+v", key, p)
 		}
 		p.Uid = binary.BigEndian.Uint64(k)
-
+		if p.Uid == 0 {
+			return p, errors.Errorf("Invalid UID with value 0 for key: %v", key)
+		}
 		if !p.HasStartUid {
 			break
 		}
diff --git a/x/keys_test.go b/x/keys_test.go
index 7441c6ff378..a96761b5958 100644
--- a/x/keys_test.go
+++ b/x/keys_test.go
@@ -27,7 +27,14 @@ import (
 
 func TestDataKey(t *testing.T) {
 	var uid uint64
-	for uid = 0; uid < 1001; uid++ {
+
+	// key with uid = 0 is invalid
+	uid = 0
+	key := DataKey("bad uid", uid)
+	_, err := Parse(key)
+	require.Error(t, err)
+
+	for uid = 1; uid < 1001; uid++ {
 		// Use the uid to derive the attribute so it has variable length and the test
 		// can verify that multiple sizes of attr work correctly.
 		sattr := fmt.Sprintf("attr:%d", uid)
@@ -58,7 +65,7 @@ func TestDataKey(t *testing.T) {
 func TestParseDataKeyWithStartUid(t *testing.T) {
 	var uid uint64
 	startUid := uint64(math.MaxUint64)
-	for uid = 0; uid < 1001; uid++ {
+	for uid = 1; uid < 1001; uid++ {
 		sattr := fmt.Sprintf("attr:%d", uid)
 		key := DataKey(sattr, uid)
 		key, err := SplitKey(key, startUid)
@@ -113,7 +120,7 @@ func TestIndexKeyWithStartUid(t *testing.T) {
 
 func TestReverseKey(t *testing.T) {
 	var uid uint64
-	for uid = 0; uid < 1001; uid++ {
+	for uid = 1; uid < 1001; uid++ {
 		sattr := fmt.Sprintf("attr:%d", uid)
 
 		key := ReverseKey(sattr, uid)
@@ -129,7 +136,7 @@ func TestReverseKey(t *testing.T) {
 func TestReverseKeyWithStartUid(t *testing.T) {
 	var uid uint64
 	startUid := uint64(math.MaxUint64)
-	for uid = 0; uid < 1001; uid++ {
+	for uid = 1; uid < 1001; uid++ {
 		sattr := fmt.Sprintf("attr:%d", uid)
 
 		key := ReverseKey(sattr, uid)
@@ -252,4 +259,10 @@ func TestBadKeys(t *testing.T) {
 	key = []byte{1, 0x00, 0x04, 1, 2}
 	_, err = Parse(key)
 	require.Error(t, err)
+
+	// key with uid = 0 is invalid
+	uid := 0
+	key = DataKey("bad uid", uint64(uid))
+	_, err = Parse(key)
+	require.Error(t, err)
 }