diff --git a/ArcFormats/ArcCommon.cs b/ArcFormats/ArcCommon.cs
index fe453f2d..9a187efc 100644
--- a/ArcFormats/ArcCommon.cs
+++ b/ArcFormats/ArcCommon.cs
@@ -291,6 +291,14 @@ namespace GameRes.Formats
             mask |= mask << 32;
             return (x << count) & mask;
         }
+
+        public static ulong PSrlD (ulong x, int count)
+        {
+            count &= 0x1F;
+            ulong mask = 0xFFFFFFFFu >> count;
+            mask |= mask << 32;
+            return (x >> count) & mask;
+        }
     }
 
     public static class Dump