diff --git a/arch/x86/lib/realmode.c b/arch/x86/lib/realmode.c
index c113393..6aa0f23 100644
--- a/arch/x86/lib/realmode.c
+++ b/arch/x86/lib/realmode.c
@@ -41,7 +41,7 @@
 	if (realmode_size > (REALMODE_MAILBOX - (char *)REALMODE_BASE)) {
 		printf("realmode switch too large (%ld bytes, max is %d)\n",
 		       realmode_size,
-		       (REALMODE_MAILBOX - (char *)REALMODE_BASE));
+		       (int)(REALMODE_MAILBOX - (char *)REALMODE_BASE));
 		return -1;
 	}