diff --git a/cmd/encryption-v1.go b/cmd/encryption-v1.go
index 0dfa2bf81..c3e5604be 100644
--- a/cmd/encryption-v1.go
+++ b/cmd/encryption-v1.go
@@ -930,26 +930,29 @@ func (o *ObjectInfo) GetDecryptedRange(rs *HTTPRangeSpec) (encOff, encLength, sk
 	}
 
 	// Assemble slice of (decrypted) part sizes in `sizes`
+	var sizes []int64
 	var decObjSize int64 // decrypted total object size
-	var partSize uint64
-	partSize, err = sio.DecryptedSize(uint64(o.Size))
-	if err != nil {
-		return
-	}
-	sizes := []int64{int64(partSize)}
-	decObjSize = sizes[0]
 	if isEncryptedMultipart(*o) {
 		sizes = make([]int64, len(o.Parts))
-		decObjSize = 0
 		for i, part := range o.Parts {
+			var partSize uint64
 			partSize, err = sio.DecryptedSize(uint64(part.Size))
 			if err != nil {
+				err = errObjectTampered
 				return
 			}
-			t := int64(partSize)
-			sizes[i] = t
-			decObjSize += t
+			sizes[i] = int64(partSize)
+			decObjSize += int64(partSize)
+		}
+	} else {
+		var partSize uint64
+		partSize, err = sio.DecryptedSize(uint64(o.Size))
+		if err != nil {
+			err = errObjectTampered
+			return
 		}
+		sizes = []int64{int64(partSize)}
+		decObjSize = sizes[0]
 	}
 
 	var off, length int64
diff --git a/cmd/encryption-v1_test.go b/cmd/encryption-v1_test.go
index f2af329f6..9cd4221d7 100644
--- a/cmd/encryption-v1_test.go
+++ b/cmd/encryption-v1_test.go
@@ -334,6 +334,66 @@ func TestDecryptObjectInfo(t *testing.T) {
 	}
 }
 
+// Tests for issue reproduced when getting the right encrypted
+// offset of the object.
+func TestGetDecryptedRange_Issue50(t *testing.T) {
+	rs, err := parseRequestRangeSpec("bytes=594870256-594870263")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	objInfo := ObjectInfo{
+		Bucket: "bucket",
+		Name:   "object",
+		Size:   595160760,
+		UserDefined: map[string]string{
+			crypto.SSEMultipart:                    "",
+			crypto.SSEIV:                           "HTexa=",
+			crypto.SSESealAlgorithm:                "DAREv2-HMAC-SHA256",
+			crypto.SSECSealedKey:                   "IAA8PGAA==",
+			ReservedMetadataPrefix + "actual-size": "594870264",
+			"content-type":                         "application/octet-stream",
+			"etag":                                 "166b1545b4c1535294ee0686678bea8c-2",
+		},
+		Parts: []objectPartInfo{
+			{
+				Number:     1,
+				Name:       "part.1",
+				ETag:       "etag1",
+				Size:       297580380,
+				ActualSize: 297435132,
+			},
+			{
+				Number:     2,
+				Name:       "part.2",
+				ETag:       "etag2",
+				Size:       297580380,
+				ActualSize: 297435132,
+			},
+		},
+	}
+
+	encOff, encLength, skipLen, seqNumber, partStart, err := objInfo.GetDecryptedRange(rs)
+	if err != nil {
+		t.Fatalf("Test: failed %s", err)
+	}
+	if encOff != 595127964 {
+		t.Fatalf("Test: expected %d, got %d", 595127964, encOff)
+	}
+	if encLength != 32796 {
+		t.Fatalf("Test: expected %d, got %d", 32796, encLength)
+	}
+	if skipLen != 32756 {
+		t.Fatalf("Test: expected %d, got %d", 32756, skipLen)
+	}
+	if seqNumber != 4538 {
+		t.Fatalf("Test: expected %d, got %d", 4538, seqNumber)
+	}
+	if partStart != 1 {
+		t.Fatalf("Test: expected %d, got %d", 1, partStart)
+	}
+}
+
 func TestGetDecryptedRange(t *testing.T) {
 	var (
 		pkgSz     = int64(64) * humanize.KiByte