diff --git a/core/src/main/java/org/bouncycastle/crypto/engines/SM2Engine.java b/core/src/main/java/org/bouncycastle/crypto/engines/SM2Engine.java
index 5bbdb0f012..22e32a3adb 100644
--- a/core/src/main/java/org/bouncycastle/crypto/engines/SM2Engine.java
+++ b/core/src/main/java/org/bouncycastle/crypto/engines/SM2Engine.java
@@ -164,7 +164,7 @@ private byte[] decrypt(byte[] in, int inOff, int inLen)
         int check = 0;
         for (int i = 0; i != c3.length; i++)
         {
-            check |= c3[i] ^ in[c1.length + c2.length + i];
+            check |= c3[i] ^ in[inOff + c1.length + c2.length + i];
         }
 
         Arrays.fill(c1, (byte)0);