diff -Naur a/hw/xfree86/ddc/ddcProperty.c b/xfree86/ddc/ddcProperty.c
--- a/hw/xfree86/ddc/ddcProperty.c	2007-01-23 05:39:16.000000000 +0000
+++ b/hw/xfree86/ddc/ddcProperty.c	2007-01-25 23:46:11.000000000 +0000
@@ -313,8 +313,11 @@
 
     preferred = PREFERRED_TIMING_MODE(DDC->features.msc);
 
-    Monitor->widthmm = 10 * DDC->features.hsize;
-    Monitor->heightmm = 10 * DDC->features.vsize;
+    /* Set display size if it was not specified in the config file */
+    if (Monitor->widthmm <= 0)
+     Monitor->widthmm = 10 * DDC->features.hsize;
+    if (Monitor->heightmm <= 0)
+     Monitor->heightmm = 10 * DDC->features.vsize;
     
     /* If this is a digital display, then we can use reduced blanking */
     if (DDC->features.input_type)