diff --git a/sys/powerpc/aim/interrupt.c b/sys/powerpc/aim/interrupt.c
index d7f489ad4e2..b4360384155 100644
--- a/sys/powerpc/aim/interrupt.c
+++ b/sys/powerpc/aim/interrupt.c
@@ -80,15 +80,17 @@ powerpc_interrupt(struct trapframe *framep)
 
 	switch (framep->exc) {
 	case EXC_EXI:
-		atomic_add_int(&td->td_intr_nesting_level, 1);
+		critical_enter();
 		PIC_DISPATCH(pic, framep);
-		atomic_subtract_int(&td->td_intr_nesting_level, 1);	
+		critical_exit();
 		break;
 
 	case EXC_DECR:
+		critical_enter();
 		atomic_add_int(&td->td_intr_nesting_level, 1);
 		decr_intr(framep);
 		atomic_subtract_int(&td->td_intr_nesting_level, 1);	
+		critical_exit();
 		break;
 
 	default:
diff --git a/sys/powerpc/booke/interrupt.c b/sys/powerpc/booke/interrupt.c
index 01ee3d9fa83..2367bf94b33 100644
--- a/sys/powerpc/booke/interrupt.c
+++ b/sys/powerpc/booke/interrupt.c
@@ -118,9 +118,11 @@ powerpc_decr_interrupt(struct trapframe *framep)
 	struct thread *td;
 
 	td = PCPU_GET(curthread);
+	critical_enter();
 	atomic_add_int(&td->td_intr_nesting_level, 1);
 	decr_intr(framep);
 	atomic_subtract_int(&td->td_intr_nesting_level, 1);
+	critical_exit();
 }
 
 /*
@@ -129,10 +131,8 @@ powerpc_decr_interrupt(struct trapframe *framep)
 void
 powerpc_extr_interrupt(struct trapframe *framep)
 {
-	struct thread *td;
 
-	td = PCPU_GET(curthread);
-	atomic_add_int(&td->td_intr_nesting_level, 1);
+	critical_enter();
 	PIC_DISPATCH(pic, framep);
-	atomic_subtract_int(&td->td_intr_nesting_level, 1);
+	critical_exit();
 }