diff --git a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/Gambatte.cs b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/Gambatte.cs
index e6c18eb3c4..4634a0f425 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/Gambatte.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/Gambatte.cs
@@ -401,7 +401,17 @@ namespace BizHawk.Emulation.Cores.Nintendo.Gameboy
 #endif
 
 		public bool IsCGBDMGMode
+#if true
+		{
+			get
+			{
+				var headerCgbCompat = LibGambatte.gambatte_cpuread(GambatteState, 0x143);
+				return (headerCgbCompat & 0x80) == 0 || (headerCgbCompat & 0x84) == 0x84;
+			}
+		}
+#else
 			=> LibGambatte.gambatte_iscgbdmg(GambatteState);
+#endif
 
 		private InputCallbackSystem _inputCallbacks = new();
 
diff --git a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/IGameboyCommon.cs b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/IGameboyCommon.cs
index 66aa8ae45a..a20c2f7335 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/IGameboyCommon.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/IGameboyCommon.cs
@@ -24,7 +24,6 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.Gameboy
 		bool IsCGBMode { get; }
 
 		/// <value><see langword="true"/> iff the emulator is currently emulating CGB in DMG compatibility mode</value>
-		/// <remarks>NOTE: this mode does not take affect until the bootrom unmaps itself</remarks>
 		bool IsCGBDMGMode { get; }
 
 		/// <summary>
diff --git a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/SameBoy/SameBoy.cs b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/SameBoy/SameBoy.cs
index a8224f7ea7..7422996869 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/SameBoy/SameBoy.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/SameBoy/SameBoy.cs
@@ -38,7 +38,17 @@ namespace BizHawk.Emulation.Cores.Nintendo.Sameboy
 			=> IsCgb; //TODO inline
 
 		public bool IsCGBDMGMode
+#if true
+		{
+			get
+			{
+				var headerCgbCompat = LibSameboy.sameboy_cpuread(SameboyState, 0x143);
+				return (headerCgbCompat & 0x80) == 0 || (headerCgbCompat & 0x84) == 0x84;
+			}
+		}
+#else
 			=> LibSameboy.sameboy_iscgbdmg(SameboyState);
+#endif
 
 		private readonly LibSameboy.InputCallback _inputcb;