diff --git a/hw/xfree86/ddc/ddcProperty.c b/hw/xfree86/ddc/ddcProperty.c
index a1650bc..9e36388 100644
--- a/hw/xfree86/ddc/ddcProperty.c
+++ b/hw/xfree86/ddc/ddcProperty.c
@@ -313,9 +313,11 @@ xf86DDCMonitorSet(int scrnIndex, MonPtr
 
     preferred = PREFERRED_TIMING_MODE(DDC->features.msc);
 
-    Monitor->widthmm = 10 * DDC->features.hsize;
-    Monitor->heightmm = 10 * DDC->features.vsize;
-    
+    if (!Monitor->widthmm) 
+	Monitor->widthmm = 10 * DDC->features.hsize;
+    if (!Monitor->heightmm)
+	Monitor->heightmm = 10 * DDC->features.vsize;
+
     /* If this is a digital display, then we can use reduced blanking */
     if (DDC->features.input_type) 
         Monitor->reducedblanking = TRUE;