diff --git a/picirq.c b/picirq.c
index 19c4f88..9c3ea0c 100644
--- a/picirq.c
+++ b/picirq.c
@@ -53,7 +53,7 @@ pic_init(void)
   outb(IO_PIC2+1, IRQ_SLAVE);		// ICW3
   // NB Automatic EOI mode doesn't tend to work on the slave.
   // Linux source code says it's "to be investigated".
-  outb(IO_PIC2+1, 0x1);			// ICW4
+  outb(IO_PIC2+1, 0x3);			// ICW4
 
   // OCW3:  0ef01prs
   //   ef:  0x = NOP, 10 = clear specific mask, 11 = set specific mask