diff --git a/ChangeLog b/ChangeLog
index a488561a3..51c211c43 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2009-05-14  Christian Franke  <franke@computer.org>
+
+	* commands/i386/pc/drivemap_int13h.S: Add missing EXT_C for symbols.
+	This fixes build on Cygwin.
+
 2009-05-14  Pavel Roskin  <proski@gnu.org>
 
 	* commands/i386/pc/drivemap_int13h.S: Eliminate unconditional
diff --git a/commands/i386/pc/drivemap_int13h.S b/commands/i386/pc/drivemap_int13h.S
index 6513411be..44f91bb56 100644
--- a/commands/i386/pc/drivemap_int13h.S
+++ b/commands/i386/pc/drivemap_int13h.S
@@ -19,7 +19,7 @@
 
 #include <grub/symbol.h>
 
-#define INT13H_OFFSET(x) ((x) - grub_drivemap_handler)
+#define INT13H_OFFSET(x) ((x) - EXT_C(grub_drivemap_handler))
 
 .code16
 
@@ -31,7 +31,7 @@ FUNCTION(grub_drivemap_handler)
 	/* Map the drive number (always in DL).  */
 	push	%ax
 	push	%bx
-	movw	$INT13H_OFFSET(grub_drivemap_mapstart), %bx
+	movw	$INT13H_OFFSET(EXT_C(grub_drivemap_mapstart)), %bx
 
 more_remaining:
 	movw	%cs:(%bx), %ax