diff --git a/hw/xfree86/common/xf86Helper.c b/hw/xfree86/common/xf86Helper.c
index 0389945a7..d03382d26 100644
--- a/hw/xfree86/common/xf86Helper.c
+++ b/hw/xfree86/common/xf86Helper.c
@@ -55,6 +55,7 @@
 #include "xf86Xinput.h"
 #include "xf86InPriv.h"
 #include "mivalidate.h"
+#include "xf86Crtc.h"
 
 /* For xf86GetClocks */
 #if defined(CSRG_BASED) || defined(__GNU__)
@@ -851,8 +852,9 @@ xf86SetDpi(ScrnInfoPtr pScrn, int x, int y)
 {
     MessageType from = X_DEFAULT;
     xf86MonPtr DDC = (xf86MonPtr) (pScrn->monitor->DDC);
-    int ddcWidthmm, ddcHeightmm;
+    int probedWidthmm, probedHeightmm;
     int widthErr, heightErr;
+    xf86OutputPtr compat = xf86CompatOutput(pScrn);
 
     /* XXX Maybe there is no need for widthmm/heightmm in ScrnInfoRec */
     pScrn->widthmm = pScrn->monitor->widthmm;
@@ -862,11 +864,15 @@ xf86SetDpi(ScrnInfoPtr pScrn, int x, int y)
         /* DDC gives display size in mm for individual modes,
          * but cm for monitor
          */
-        ddcWidthmm = DDC->features.hsize * 10;  /* 10mm in 1cm */
-        ddcHeightmm = DDC->features.vsize * 10; /* 10mm in 1cm */
+        probedWidthmm = DDC->features.hsize * 10;  /* 10mm in 1cm */
+        probedHeightmm = DDC->features.vsize * 10; /* 10mm in 1cm */
+    }
+    else if (compat && compat->mm_width > 0 && compat->mm_height > 0) {
+        probedWidthmm = compat->mm_width;
+        probedHeightmm = compat->mm_height;
     }
     else {
-        ddcWidthmm = ddcHeightmm = 0;
+        probedWidthmm = probedHeightmm = 0;
     }
 
     if (monitorResolution > 0) {
@@ -892,15 +898,15 @@ xf86SetDpi(ScrnInfoPtr pScrn, int x, int y)
                    pScrn->widthmm, pScrn->heightmm);
 
         /* Warn if config and probe disagree about display size */
-        if (ddcWidthmm && ddcHeightmm) {
+        if (probedWidthmm && probedHeightmm) {
             if (pScrn->widthmm > 0) {
-                widthErr = abs(ddcWidthmm - pScrn->widthmm);
+                widthErr = abs(probedWidthmm - pScrn->widthmm);
             }
             else {
                 widthErr = 0;
             }
             if (pScrn->heightmm > 0) {
-                heightErr = abs(ddcHeightmm - pScrn->heightmm);
+                heightErr = abs(probedHeightmm - pScrn->heightmm);
             }
             else {
                 heightErr = 0;
@@ -909,17 +915,17 @@ xf86SetDpi(ScrnInfoPtr pScrn, int x, int y)
                 /* Should include config file name for monitor here */
                 xf86DrvMsg(pScrn->scrnIndex, X_WARNING,
                            "Probed monitor is %dx%d mm, using Displaysize %dx%d mm\n",
-                           ddcWidthmm, ddcHeightmm, pScrn->widthmm,
+                           probedWidthmm, probedHeightmm, pScrn->widthmm,
                            pScrn->heightmm);
             }
         }
     }
-    else if (ddcWidthmm && ddcHeightmm) {
+    else if (probedWidthmm && probedHeightmm) {
         from = X_PROBED;
         xf86DrvMsg(pScrn->scrnIndex, from, "Display dimensions: (%d, %d) mm\n",
-                   ddcWidthmm, ddcHeightmm);
-        pScrn->widthmm = ddcWidthmm;
-        pScrn->heightmm = ddcHeightmm;
+                   probedWidthmm, probedHeightmm);
+        pScrn->widthmm = probedWidthmm;
+        pScrn->heightmm = probedHeightmm;
         if (pScrn->widthmm > 0) {
             pScrn->xDpi =
                 (int) ((double) pScrn->virtualX * MMPERINCH / pScrn->widthmm);
diff --git a/hw/xfree86/modes/xf86Crtc.c b/hw/xfree86/modes/xf86Crtc.c
index c6e89e66f..202791774 100644
--- a/hw/xfree86/modes/xf86Crtc.c
+++ b/hw/xfree86/modes/xf86Crtc.c
@@ -3256,8 +3256,10 @@ xf86OutputSetEDID(xf86OutputPtr output, xf86MonPtr edid_mon)
     free(output->MonInfo);
 
     output->MonInfo = edid_mon;
-    output->mm_width = 0;
-    output->mm_height = 0;
+    if (edid_mon) {
+        output->mm_width = 0;
+        output->mm_height = 0;
+    }
 
     if (debug_modes) {
         xf86DrvMsg(scrn->scrnIndex, X_INFO, "EDID for output %s\n",
diff --git a/hw/xfree86/modes/xf86RandR12.c b/hw/xfree86/modes/xf86RandR12.c
index 50cbd043e..d4651f4e8 100644
--- a/hw/xfree86/modes/xf86RandR12.c
+++ b/hw/xfree86/modes/xf86RandR12.c
@@ -806,6 +806,12 @@ xf86RandR12CreateScreenResources(ScreenPtr pScreen)
                 mmWidth = output->conf_monitor->mon_width;
                 mmHeight = output->conf_monitor->mon_height;
             }
+            else if (output &&
+                (output->mm_width > 0 &&
+                 output->mm_height > 0)) {
+                mmWidth = output->mm_width;
+                mmHeight = output->mm_height;
+            }
             else {
                 /*
                  * Otherwise, just set the screen to DEFAULT_DPI