diff --git a/controller/atomic.go b/controller/atomic.go
index 2ee4b1d1..882bb253 100644
--- a/controller/atomic.go
+++ b/controller/atomic.go
@@ -10,7 +10,7 @@ type aint struct{ v uintptr }
 
 func (a *aint) add(d int) int {
 	if d < 0 {
-		return int(atomic.AddUintptr(&a.v, ^uintptr(d-1)))
+		return int(atomic.AddUintptr(&a.v, ^uintptr((d*-1)-1)))
 	}
 	return int(atomic.AddUintptr(&a.v, uintptr(d)))
 }
diff --git a/controller/atomic_test.go b/controller/atomic_test.go
new file mode 100644
index 00000000..b26152f6
--- /dev/null
+++ b/controller/atomic_test.go
@@ -0,0 +1,19 @@
+package controller
+
+import "testing"
+
+func TestAtomicInt(t *testing.T) {
+	var x aint
+	x.set(10)
+	if x.get() != 10 {
+		t.Fatalf("expected %v, got %v", 10, x.get())
+	}
+	x.add(-9)
+	if x.get() != 1 {
+		t.Fatalf("expected %v, got %v", 1, x.get())
+	}
+	x.add(-1)
+	if x.get() != 0 {
+		t.Fatalf("expected %v, got %v", 0, x.get())
+	}
+}