diff --git a/sm4/xts_arm64.s b/sm4/xts_arm64.s
index ea3446e..651ebb6 100644
--- a/sm4/xts_arm64.s
+++ b/sm4/xts_arm64.s
@@ -282,7 +282,7 @@ encNibblesEnc4Blocks:
 
 xtsSm4EncSingles:
 	CMP	$16, srcPtrLen
-	BLT	xtsSm4EncDone
+	BLT	xtsSm4EncTail
 	SUB	$16, srcPtrLen
 
 	loadOneBlock
@@ -303,6 +303,69 @@ encSinglesEnc4Blocks:
 	mul2Inline
 	B	xtsSm4EncSingles
 
+xtsSm4EncTail:
+	CBZ	srcPtrLen, xtsSm4EncDone
+	SUB $16, dstPtr, R7
+	MOVD R7, R9
+	MOVD RSP, R8
+	VLD1 (R7), [B0.B16]
+	VST1 [B0.B16], (R8)
+
+	TBZ	$3, srcPtrLen, less_than8
+	MOVD.P 8(srcPtr), R11
+	MOVD.P R11, 8(R8)
+	MOVD.P 8(R7), R12
+	MOVD.P R12, 8(dstPtr)
+
+less_than8:
+	TBZ	$2, srcPtrLen, less_than4
+	MOVWU.P 4(srcPtr), R11
+	MOVWU.P R11, 4(R8)
+	MOVWU.P 4(R7), R12
+	MOVWU.P R12, 4(dstPtr)
+
+less_than4:
+	TBZ	$1, srcPtrLen, less_than2
+	MOVHU.P 2(srcPtr), R11
+	MOVHU.P R11, 2(R8)
+	MOVHU.P 2(R7), R12
+	MOVHU.P R12, 2(dstPtr)
+
+less_than2:
+	TBZ	$0, srcPtrLen, xtsSm4EncTailEnc
+	MOVBU (srcPtr), R11
+	MOVBU R11, (R8)
+	MOVBU (R7), R12
+	MOVBU R12, (dstPtr)
+
+xtsSm4EncTailEnc:
+	VLD1 (RSP), [B0.B16]
+	VEOR TW.B16, B0.B16, B0.B16
+	VREV32 B0.B16, B0.B16
+	VMOV B0.S[1], B1.S[0]
+	VMOV B0.S[2], B2.S[0]
+	VMOV B0.S[3], B3.S[0]
+
+	MOVD rkSave, rk
+	EOR R13, R13
+
+tailEncLoop:
+		SM4_ROUND(rk, R19, K0, K1, K2, B0, B1, B2, B3)
+		SM4_ROUND(rk, R19, K0, K1, K2, B1, B2, B3, B0)
+		SM4_ROUND(rk, R19, K0, K1, K2, B2, B3, B0, B1)
+		SM4_ROUND(rk, R19, K0, K1, K2, B3, B0, B1, B2)
+		ADD $1, R13
+		CMP $8, R13
+		BNE tailEncLoop
+
+	VMOV B2.S[0], B3.S[1]
+	VMOV B1.S[0], B3.S[2]
+	VMOV B0.S[0], B3.S[3]
+	VREV32 B3.B16, B3.B16
+
+	VEOR TW.B16, B3.B16, B3.B16
+	VST1 [B3.B16], (R9)
+
 xtsSm4EncDone:
 	VST1 [TW.B16], (twPtr)
 	RET