diff --git a/src/i810_driver.c b/src/i810_driver.c
index 22635c86..cd6d9d7d 100644
--- a/src/i810_driver.c
+++ b/src/i810_driver.c
@@ -1186,14 +1186,13 @@ I810MapMem(ScrnInfoPtr pScrn)
    long i;
 
    for (i = 2; i < pI810->FbMapSize; i <<= 1) ;
-   pI810->FbMapSize = i;
 
    if (!I810MapMMIO(pScrn))
       return FALSE;
 
    pI810->FbBase = xf86MapPciMem(pScrn->scrnIndex, VIDMEM_FRAMEBUFFER,
 				 pI810->PciTag,
-				 pI810->LinearAddr, pI810->FbMapSize);
+				 pI810->LinearAddr, i);
    if (!pI810->FbBase)
       return FALSE;