diff --git a/src/ibm.h b/src/ibm.h
index 38cf6e857..3b2720941 100644
--- a/src/ibm.h
+++ b/src/ibm.h
@@ -374,7 +374,7 @@ extern int pic_intpending;
 
 
 extern int disctime;
-extern wchar_t discfns[4][256];
+extern wchar_t discfns[4][512];
 extern int driveempty[4];
 
 #define MDA ((gfxcard==GFX_MDA || gfxcard==GFX_HERCULES || gfxcard==GFX_HERCULESPLUS || gfxcard==GFX_INCOLOR || gfxcard==GFX_GENIUS) && (romset<ROM_TANDY || romset>=ROM_IBMAT))