diff --git a/dlls/winmm/mmio.c b/dlls/winmm/mmio.c
index 75439a4..5c9fc13 100644
--- a/dlls/winmm/mmio.c
+++ b/dlls/winmm/mmio.c
@@ -880,7 +880,7 @@ LONG WINAPI mmioSeek(HMMIO hmmio, LONG lOffset, INT iOrigin)
 	return -1;
     }
 
-    if (offset && offset >= wm->dwFileSize && wm->info.fccIOProc != FOURCC_MEM) {
+    if (offset && offset >= wm->dwFileSize && wm->info.fccIOProc == FOURCC_DOS) {
         /* should check that write mode exists */
         if (MMIO_Flush(wm, 0) != MMSYSERR_NOERROR)
             return -1;