diff --git a/reactos/ntoskrnl/fsrtl/fastio.c b/reactos/ntoskrnl/fsrtl/fastio.c
index 78ac48e57bd..1b6c21c89a7 100644
--- a/reactos/ntoskrnl/fsrtl/fastio.c
+++ b/reactos/ntoskrnl/fsrtl/fastio.c
@@ -198,8 +198,8 @@ FsRtlCopyRead(IN PFILE_OBJECT FileObject,
 
             if (IoStatus->Status != STATUS_END_OF_FILE)
             {
-                ASSERT(FcbHeader->FileSize.QuadPart >=
-                       FileOffset->QuadPart + IoStatus->Information);
+                ASSERT((ULONGLONG)FcbHeader->FileSize.QuadPart >=
+                       (FileOffset->QuadPart + IoStatus->Information));
             }
         }
         else
@@ -219,8 +219,8 @@ FsRtlCopyRead(IN PFILE_OBJECT FileObject,
             if (Result == TRUE)
             {
                 ASSERT((IoStatus->Status == STATUS_END_OF_FILE) ||
-                       ((LONGLONG)(FileOffset->QuadPart + IoStatus->Information) <=
-                        FcbHeader->FileSize.QuadPart));
+                       ((FileOffset->QuadPart + IoStatus->Information) <=
+                        (ULONGLONG)FcbHeader->FileSize.QuadPart));
             }
         }