diff --git a/BizHawk.Emulation.Cores/Consoles/Sega/gpgx/GPGXControlConverter.cs b/BizHawk.Emulation.Cores/Consoles/Sega/gpgx/GPGXControlConverter.cs
index ce610f7228..f1af5af62f 100644
--- a/BizHawk.Emulation.Cores/Consoles/Sega/gpgx/GPGXControlConverter.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Sega/gpgx/GPGXControlConverter.cs
@@ -97,7 +97,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Sega.gpgx
 			new CName("XE E2", LibGPGX.INPUT_KEYS.INPUT_XE_E2),
 		};
 
-		static ControllerDefinition.FloatRange MouseRange = new ControllerDefinition.FloatRange(-512, 0, 511);
+		static ControllerDefinition.FloatRange MouseRange = new ControllerDefinition.FloatRange(-256, 0, 255);
 		// lightgun needs to be transformed to match the current screen resolution
 		static ControllerDefinition.FloatRange LightgunRange = new ControllerDefinition.FloatRange(0, 5000, 10000);