diff --git a/reactos/dll/win32/advapi32/sec/misc.c b/reactos/dll/win32/advapi32/sec/misc.c
index 7e8b3fd0c5f..2510f39ae7a 100644
--- a/reactos/dll/win32/advapi32/sec/misc.c
+++ b/reactos/dll/win32/advapi32/sec/misc.c
@@ -1200,8 +1200,11 @@ LookupAccountSidW(LPCWSTR pSystemName,
 				else
 				{
 					*pdwDomainName = dwSrcLen;
-					RtlCopyMemory ( pDomainName, ReferencedDomain->Domains[0].Name.Buffer, ReferencedDomain->Domains[0].Name.Length );
-					                pDomainName[ReferencedDomain->Domains[0].Name.Length / sizeof(WCHAR)] = L'\0';
+					if (pDomainName)
+					{
+					    RtlCopyMemory ( pDomainName, ReferencedDomain->Domains[0].Name.Buffer, ReferencedDomain->Domains[0].Name.Length );
+					    pDomainName[ReferencedDomain->Domains[0].Name.Length / sizeof(WCHAR)] = L'\0';
+					}
 				}
 			}
 		}