diff --git a/defs.h b/defs.h
index 1c28cc0..fead1d2 100644
--- a/defs.h
+++ b/defs.h
@@ -40,8 +40,6 @@ int strncmp(const char *p, const char *q, uint n);
 void syscall(void);
 
 // picirq.c
-extern ushort irq_mask_8259A;
-void irq_setmask_8259A(ushort mask);
 void pic_init(void);
 
 // mp.c
diff --git a/picirq.c b/picirq.c
index e774e6d..9fd7167 100644
--- a/picirq.c
+++ b/picirq.c
@@ -12,7 +12,24 @@
 
 // Current IRQ mask.
 // Initial IRQ mask has interrupt 2 enabled (for slave 8259A).
-ushort irq_mask_8259A = 0xFFFF & ~(1<<IRQ_SLAVE);
+static ushort irq_mask_8259A = 0xFFFF & ~(1<<IRQ_SLAVE);
+
+static void
+irq_setmask_8259A(ushort mask)
+{
+  int i;
+  irq_mask_8259A = mask;
+
+  outb(IO_PIC1+1, (char)mask);
+  outb(IO_PIC2+1, (char)(mask >> 8));
+
+  cprintf("%d: enabled interrupts:", cpu());
+
+  for (i = 0; i < 16; i++)
+    if (~mask & (1<<i))
+      cprintf(" %d", i);
+  cprintf("\n");
+}
 
 /* Initialize the 8259A interrupt controllers. */
 void
@@ -68,20 +85,3 @@ pic_init(void)
   if (irq_mask_8259A != 0xFFFF)
     irq_setmask_8259A(irq_mask_8259A);
 }
-
-void
-irq_setmask_8259A(ushort mask)
-{
-  int i;
-  irq_mask_8259A = mask;
-
-  outb(IO_PIC1+1, (char)mask);
-  outb(IO_PIC2+1, (char)(mask >> 8));
-
-  cprintf("%d: enabled interrupts:", cpu());
-
-  for (i = 0; i < 16; i++)
-    if (~mask & (1<<i))
-      cprintf(" %d", i);
-  cprintf("\n");
-}