diff --git a/hw/xfree86/common/xf86Mode.c b/hw/xfree86/common/xf86Mode.c
index 16dd529e3..136cd15d0 100644
--- a/hw/xfree86/common/xf86Mode.c
+++ b/hw/xfree86/common/xf86Mode.c
@@ -230,6 +230,8 @@ xf86ModeStatusToString(ModeStatus status)
         return "monitor doesn't support reduced blanking";
     case MODE_BANDWIDTH:
         return "mode requires too much memory bandwidth";
+    case MODE_DUPLICATE:
+        return "the same mode has been added";
     case MODE_BAD:
         return "unknown reason";
     case MODE_ERROR:
diff --git a/hw/xfree86/drivers/modesetting/drmmode_display.c b/hw/xfree86/drivers/modesetting/drmmode_display.c
index 623961ff6..1c1d79f30 100644
--- a/hw/xfree86/drivers/modesetting/drmmode_display.c
+++ b/hw/xfree86/drivers/modesetting/drmmode_display.c
@@ -2843,7 +2843,7 @@ static DisplayModePtr
 drmmode_output_add_gtf_modes(xf86OutputPtr output, DisplayModePtr Modes)
 {
     xf86MonPtr mon = output->MonInfo;
-    DisplayModePtr i, m, preferred = NULL;
+    DisplayModePtr i, j, m, preferred = NULL;
     int max_x = 0, max_y = 0;
     float max_vrefresh = 0.0;
 
@@ -2875,6 +2875,17 @@ drmmode_output_add_gtf_modes(xf86OutputPtr output, DisplayModePtr Modes)
             i->VDisplay >= preferred->VDisplay &&
             xf86ModeVRefresh(i) >= xf86ModeVRefresh(preferred))
             i->status = MODE_VSYNC;
+        if (preferred && xf86ModeVRefresh(i) > 0.0) {
+            i->Clock = i->Clock * xf86ModeVRefresh(preferred) / xf86ModeVRefresh(i);
+            i->VRefresh = xf86ModeVRefresh(preferred);
+        }
+        for (j = m; j != i; j = j->next) {
+            if (!strcmp(i->name, j->name) &&
+                xf86ModeVRefresh(i) * (1 + SYNC_TOLERANCE) >= xf86ModeVRefresh(j) &&
+                xf86ModeVRefresh(i) * (1 - SYNC_TOLERANCE) <= xf86ModeVRefresh(j)) {
+                i->status = MODE_DUPLICATE;
+            }
+        }
     }
 
     xf86PruneInvalidModes(output->scrn, &m, FALSE);
diff --git a/include/displaymode.h b/include/displaymode.h
index ad01b87ec..561087717 100644
--- a/include/displaymode.h
+++ b/include/displaymode.h
@@ -47,6 +47,7 @@ typedef enum {
     MODE_ONE_SIZE,              /* only one resolution is supported */
     MODE_NO_REDUCED,            /* monitor doesn't accept reduced blanking */
     MODE_BANDWIDTH,             /* mode requires too much memory bandwidth */
+    MODE_DUPLICATE,             /* mode is duplicated */
     MODE_BAD = -2,              /* unspecified reason */
     MODE_ERROR = -1             /* error condition */
 } ModeStatus;