diff --git a/de4dot.code/deobfuscators/dotNET_Reactor/v4/EncryptedResource.cs b/de4dot.code/deobfuscators/dotNET_Reactor/v4/EncryptedResource.cs
index 32d14b9a..b2ea398f 100644
--- a/de4dot.code/deobfuscators/dotNET_Reactor/v4/EncryptedResource.cs
+++ b/de4dot.code/deobfuscators/dotNET_Reactor/v4/EncryptedResource.cs
@@ -210,7 +210,8 @@ namespace de4dot.code.deobfuscators.dotNET_Reactor.v4 {
 					return false;
 
 				if (DotNetUtils.GetMethod(method.DeclaringType, "System.Security.Cryptography.SymmetricAlgorithm", "()") != null)
-					return false;
+					if (localTypes.Exists("System.UInt64"))
+						return false;
 
 				if (!localTypes.Exists("System.Security.Cryptography.RijndaelManaged") &&
 					!localTypes.Exists("System.Security.Cryptography.AesManaged") &&