diff --git a/packages/fcl-process/src/win/process.inc b/packages/fcl-process/src/win/process.inc
index 66759198f9..7183015348 100644
--- a/packages/fcl-process/src/win/process.inc
+++ b/packages/fcl-process/src/win/process.inc
@@ -384,7 +384,7 @@ end;
 
 function TIODescriptor.SysNullFileName: string;
 begin
-  result:='NULL';
+  result:='NUL';
 end;
 
 function TIODescriptor.SysIsTypeSupported(AValue: TIOType): Boolean;
diff --git a/packages/fcl-process/src/wince/process.inc b/packages/fcl-process/src/wince/process.inc
index 1c809fd397..0bbe3ff905 100644
--- a/packages/fcl-process/src/wince/process.inc
+++ b/packages/fcl-process/src/wince/process.inc
@@ -409,7 +409,7 @@ end;
 
 function TIODescriptor.SysNullFileName: string;
 begin
-  result:='NULL';
+  result:='NUL';
 end;
 
 function TIODescriptor.SysIsTypeSupported(AValue: TIOType): Boolean;