diff --git a/reactos/ntoskrnl/io/iomgr/iomgr.c b/reactos/ntoskrnl/io/iomgr/iomgr.c
index 648114376ce..9434ff286c2 100644
--- a/reactos/ntoskrnl/io/iomgr/iomgr.c
+++ b/reactos/ntoskrnl/io/iomgr/iomgr.c
@@ -502,7 +502,7 @@ IoInitSystem(IN PLOADER_PARAMETER_BLOCK LoaderBlock)
     /* Assign drive letters */
     IoAssignDriveLetters(LoaderBlock,
                          &NtBootPath,
-                         RootString.Buffer,
+                         (PUCHAR)RootString.Buffer,
                          &RootString);
 
     /* Update system root */