diff --git a/ChangeLog b/ChangeLog
index b2ffa69fa..b1c904115 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+1999-11-16  OKUJI Yoshinori  <okuji@kuicr.kyoto-u.ac.jp>
+
+	From Pavel Roskin:
+	* stage1/stage1.S: Check for the API subset support bitmap
+	returned by INT 13 AH=48h, and jump to chs_mode if AH=42h is not
+	supported.
+	
 1999-11-13  OKUJI Yoshinori  <okuji@kuicr.kyoto-u.ac.jp>
 
 	* stage2/builtins.c (install_func): When using a Stage 1.5, set
diff --git a/stage1/stage1.S b/stage1/stage1.S
index 54bcfe882..a28adee67 100644
--- a/stage1/stage1.S
+++ b/stage1/stage1.S
@@ -147,7 +147,11 @@ real_start:
 	jc	chs_mode
 	cmpw	$0xaa55, %bx
 	jne	chs_mode
-	
+
+	/* check if AH=0x42 is supported */
+	andw	$1, %cx
+	jz	chs_mode
+		
 	/* get the geometry (limited to 2TB!) */
 	movb	$0x48, %ah
 	movw	$STAGE1_DRP_ADDR, %si