diff --git a/ntoskrnl/cc/copy.c b/ntoskrnl/cc/copy.c
index d228a981ea2..357e98162e6 100644
--- a/ntoskrnl/cc/copy.c
+++ b/ntoskrnl/cc/copy.c
@@ -556,16 +556,13 @@ CcCopyWrite (
     if (!SharedCacheMap)
         return FALSE;
 
-    /* FIXME: Honor FileObject FO_WRITE_THROUGH flag */
     ASSERT((FileOffset->QuadPart + Length) <= SharedCacheMap->SectionSize.QuadPart);
 
-    ASSERT((FileObject->Flags & FO_WRITE_THROUGH) == 0);
-
     CurrentOffset = FileOffset->QuadPart;
     while(CurrentOffset < WriteEnd)
     {
         ULONG VacbOffset = CurrentOffset % VACB_MAPPING_GRANULARITY;
-        ULONG VacbLength = min(Length, VACB_MAPPING_GRANULARITY - VacbOffset);
+        ULONG VacbLength = min(WriteEnd - CurrentOffset, VACB_MAPPING_GRANULARITY - VacbOffset);
 
         Status = CcRosGetVacb(SharedCacheMap, CurrentOffset, &Vacb);
         if (!NT_SUCCESS(Status))
@@ -585,7 +582,6 @@ CcCopyWrite (
 
             Buffer = (PVOID)((ULONG_PTR)Buffer + VacbLength);
             CurrentOffset += VacbLength;
-            Length -= VacbLength;
 
             /* Tell Mm */
             Status = MmMakePagesDirty(NULL, Add2Ptr(Vacb->BaseAddress, VacbOffset), VacbLength);
@@ -600,6 +596,10 @@ CcCopyWrite (
         _SEH2_END;
     }
 
+    /* Flush if needed */
+    if (FileObject->Flags & FO_WRITE_THROUGH)
+        CcFlushCache(FileObject->SectionObjectPointer, FileOffset, Length, NULL);
+
     return TRUE;
 }
 
@@ -757,7 +757,7 @@ CcZeroData (
     Length = EndOffset->QuadPart - StartOffset->QuadPart;
     WriteOffset.QuadPart = StartOffset->QuadPart;
 
-    if (!SharedCacheMap || (FileObject->Flags & FO_WRITE_THROUGH))
+    if (!SharedCacheMap)
     {
         /* Make this a non-cached write */
         IO_STATUS_BLOCK Iosb;
@@ -848,5 +848,9 @@ CcZeroData (
         _SEH2_END;
     }
 
+    /* Flush if needed */
+    if (FileObject->Flags & FO_WRITE_THROUGH)
+        CcFlushCache(FileObject->SectionObjectPointer, StartOffset, EndOffset->QuadPart - StartOffset->QuadPart, NULL);
+
     return TRUE;
 }