diff --git a/common/hw-gfx-gma-config.ads.template b/common/hw-gfx-gma-config.ads.template
index ccc5c1a..357b93f 100644
--- a/common/hw-gfx-gma-config.ads.template
+++ b/common/hw-gfx-gma-config.ads.template
@@ -248,4 +248,9 @@
             Secondary   => 4096,
             Tertiary    => 4096));
 
+   ----------------------------------------------------------------------------
+
+   HDMI_Max_Clock_24bpp : constant Frequency_Type :=
+     (if CPU >= Haswell then 300_000_000 else 225_000_000);
+
 end HW.GFX.GMA.Config;
diff --git a/common/hw-gfx-gma.adb b/common/hw-gfx-gma.adb
index c50d943..d156494 100644
--- a/common/hw-gfx-gma.adb
+++ b/common/hw-gfx-gma.adb
@@ -237,6 +237,23 @@
             if Port_Cfg.Mode.BPC = Auto_BPC then
                Port_Cfg.Mode.BPC := Connector_Info.Default_BPC (Port_Cfg);
             end if;
+            if Port_Cfg.Display = HDMI then
+               declare
+                  pragma Assert (Config.HDMI_Max_Clock_24bpp * 8
+                                 / Port_Cfg.Mode.BPC >= Frequency_Type'First);
+                  Max_Dotclock : constant Frequency_Type :=
+                     Config.HDMI_Max_Clock_24bpp * 8 / Port_Cfg.Mode.BPC;
+               begin
+                  if Port_Cfg.Mode.Dotclock > Max_Dotclock then
+                     pragma Debug (Debug.Put ("Dotclock "));
+                     pragma Debug (Debug.Put_Int64 (Port_Cfg.Mode.Dotclock));
+                     pragma Debug (Debug.Put (" too high, limiting to "));
+                     pragma Debug (Debug.Put_Int64 (Max_Dotclock));
+                     pragma Debug (Debug.Put_Line ("."));
+                     Port_Cfg.Mode.Dotclock := Max_Dotclock;
+                  end if;
+               end;
+            end if;
          end;
       else
          Port_Cfg := Port_Config'