diff --git a/sys/alpha/alpha/interrupt.c b/sys/alpha/alpha/interrupt.c
index 4f60ddf44f0f..c85e08d857bc 100644
--- a/sys/alpha/alpha/interrupt.c
+++ b/sys/alpha/alpha/interrupt.c
@@ -75,6 +75,7 @@ interrupt(a0, a1, a2, framep)
 	struct trapframe *framep;
 {
 
+	atomic_add_int(&intr_nesting_level, 1);
 	{
 		struct proc* p = curproc;
 		if (!p) p = &proc0;
@@ -134,6 +135,7 @@ interrupt(a0, a1, a2, framep)
 		    a0, a1, a2);
 		/* NOTREACHED */
 	}
+	atomic_subtract_int(&intr_nesting_level, 1);
 }
 
 void
diff --git a/sys/alpha/alpha/ipl_funcs.c b/sys/alpha/alpha/ipl_funcs.c
index ab8a83545e39..d13c47adb342 100644
--- a/sys/alpha/alpha/ipl_funcs.c
+++ b/sys/alpha/alpha/ipl_funcs.c
@@ -127,6 +127,7 @@ do_sir()
     u_int32_t pend;
     int i;
 
+    atomic_add_int(&intr_nesting_level, 1);
     splsoft();
     while ((pend = atomic_readandclear(&ipending)) != 0) {
 	for (i = 0; pend && i < 32; i++) {
@@ -139,6 +140,7 @@ do_sir()
 	    }
 	}
     }
+    atomic_subtract_int(&intr_nesting_level, 1);
 }
 
 #define GENSET(name, ptr, bit)			\
diff --git a/sys/alpha/include/cpu.h b/sys/alpha/include/cpu.h
index b9ff12de5b60..12436a15e2ba 100644
--- a/sys/alpha/include/cpu.h
+++ b/sys/alpha/include/cpu.h
@@ -65,11 +65,7 @@ struct clockframe {
 #define	CLKF_BASEPRI(framep)						\
 	(((framep)->cf_tf.tf_regs[FRAME_PS] & ALPHA_PSL_IPL_MASK) == 0)
 #define	CLKF_PC(framep)		((framep)->cf_tf.tf_regs[FRAME_PC])
-/*
- * XXX No way to accurately tell if we were in interrupt mode before taking
- * clock interrupt.
- */
-#define	CLKF_INTR(framep)	(0)
+#define	CLKF_INTR(framep)	(intr_nesting_level >= 2)
 
 /*
  * Preempt the current process if in interrupt from user mode,
@@ -96,6 +92,7 @@ struct clockframe {
 
 #ifdef KERNEL
 u_int32_t astpending;		/* need to trap before returning to user mode */
+u_int32_t intr_nesting_level;	/* bookeeping only; counts software intr */
 u_int32_t want_resched;		/* resched() was called */
 #endif