diff --git a/src/mess/machine/msx.c b/src/mess/machine/msx.c
index 54d76cf38fb..8df2039e0ad 100644
--- a/src/mess/machine/msx.c
+++ b/src/mess/machine/msx.c
@@ -858,6 +858,20 @@ void msx_state::msx_memory_init()
 
 			size = layout->size;
 			option = layout->option;
+			
+			if (layout->type != SLOT_CARTRIDGE1 && layout->type != SLOT_CARTRIDGE2)
+			{
+				int size_tmp = 0;
+				if (size < 0x4000)
+					size_tmp = 0x4000;
+				else if (size > 0x10000)
+					size_tmp = 0x10000;
+				else
+					size_tmp = size;
+				int extent_tmp = size_tmp / 0x4000;
+				if (extent_tmp != extent)
+					fatalerror("incorrect MSX_LAYOUT_SLOT configuration - expected extent %d but found %d\n", extent, extent_tmp);
+			}
 
 			if (VERBOSE)
 			{