diff --git a/lib_m68k/interrupts.c b/lib_m68k/interrupts.c
index 2dc079b..133494f 100644
--- a/lib_m68k/interrupts.c
+++ b/lib_m68k/interrupts.c
@@ -61,7 +61,7 @@
  */
 void irq_install_handler (int vec, interrupt_handler_t * handler, void *arg)
 {
-	if ((vec < 0) || (vec > NR_IRQS)) {
+	if ((vec < 0) || (vec >= NR_IRQS)) {
 		printf ("irq_install_handler: wrong interrupt vector %d\n",
 			vec);
 		return;
@@ -73,7 +73,7 @@
 
 void irq_free_handler (int vec)
 {
-	if ((vec < 0) || (vec > NR_IRQS)) {
+	if ((vec < 0) || (vec >= NR_IRQS)) {
 		return;
 	}