diff --git a/Decoder/AOpCodeSimdImm.cs b/Decoder/AOpCodeSimdImm.cs
index 2959aee..e7dfe62 100644
--- a/Decoder/AOpCodeSimdImm.cs
+++ b/Decoder/AOpCodeSimdImm.cs
@@ -88,7 +88,14 @@ namespace ChocolArm64.Decoder
 
         private static long ShlOnes(long Value, int Shift)
         {
-            return Value << Shift | (long)(ulong.MaxValue >> (64 - Shift));
+            if (Shift != 0)
+            {
+                return Value << Shift | (long)(ulong.MaxValue >> (64 - Shift));
+            }
+            else
+            {
+                return Value;
+            }
         }
     }
 }
\ No newline at end of file
diff --git a/Instruction/AInstEmitSimdShift.cs b/Instruction/AInstEmitSimdShift.cs
index bffed57..24d35ab 100644
--- a/Instruction/AInstEmitSimdShift.cs
+++ b/Instruction/AInstEmitSimdShift.cs
@@ -58,7 +58,7 @@ namespace ChocolArm64.Instruction
 
             int Shift = Op.Imm - (8 << Op.Size);
 
-            ulong Mask = ulong.MaxValue >> (64 - Shift);            
+            ulong Mask = Shift != 0 ? ulong.MaxValue >> (64 - Shift) : 0;            
 
             for (int Index = 0; Index < (Bytes >> Op.Size); Index++)
             {