diff --git a/ana/prediction_test.go b/ana/prediction_test.go
index d5b7b04..777e6db 100644
--- a/ana/prediction_test.go
+++ b/ana/prediction_test.go
@@ -32,6 +32,7 @@ func TestPredictionPredict(t *testing.T) {
 	}
 	from := time.Now()
 	these := []time.Time{time.Now().Add(time.Hour * 24 * 365 / 12)}
+	theseK := these.Format("2006-01")
 	_, _ = inc, double
 
 	cases := map[string]struct {
@@ -39,7 +40,9 @@ func TestPredictionPredict(t *testing.T) {
 		given      ledger.Balances
 		want       ledger.Register
 	}{
-		"empty": {},
+		"empty": {
+			want: ledger.Balances{theseK: {}},
+		},
 	}
 
 	for name, d := range cases {