diff --git a/DotN64/CPU/VR4300/VR4300.cs b/DotN64/CPU/VR4300/VR4300.cs
index af9efee..0de9c6d 100644
--- a/DotN64/CPU/VR4300/VR4300.cs
+++ b/DotN64/CPU/VR4300/VR4300.cs
@@ -332,7 +332,7 @@ namespace DotN64.CPU
                 case AccessSize.Word:
                     return ReadSysAD(physicalAddress);
                 case AccessSize.DoubleWord:
-                    return ReadSysAD(physicalAddress) << 32 | ReadSysAD(physicalAddress + sizeof(uint));
+                    return (ulong)ReadSysAD(physicalAddress) << 32 | (ulong)ReadSysAD(physicalAddress + sizeof(uint));
                 default:
                     throw new ArgumentException("Invalid system bus access size.", nameof(size));
             }