diff --git a/cmd/influxd/server_integration_test.go b/cmd/influxd/server_integration_test.go
index 49963b58044..8a8c31024b9 100644
--- a/cmd/influxd/server_integration_test.go
+++ b/cmd/influxd/server_integration_test.go
@@ -367,7 +367,7 @@ func runTestsData(t *testing.T, testName string, nodes Cluster, database, retent
 			name:     "sum aggregation",
 			query:    `SELECT sum(value) FROM cpu WHERE time >= '2000-01-01 00:00:05' AND time <= '2000-01-01T00:00:10Z' GROUP BY time(10s), region`,
 			queryDb:  "%DB%",
-			expected: `{"results":[{"series":[{"name":"cpu","tags":{"region":"us-east"},"columns":["time","sum"],"values":[["2000-01-01T00:00:00Z",30]]}]}]}`,
+			expected: `{"results":[{"series":[{"name":"cpu","tags":{"region":"us-east"},"columns":["time","sum"],"values":[["2000-01-01T00:00:00Z",null],["2000-01-01T00:00:10Z",30]]}]}]}`,
 		},
 		{
 			write: `{"database" : "%DB%", "retentionPolicy" : "%RP%", "points": [
diff --git a/influxql/engine.go b/influxql/engine.go
index f2d63da74aa..322786ac772 100644
--- a/influxql/engine.go
+++ b/influxql/engine.go
@@ -98,7 +98,8 @@ func (m *MapReduceJob) Execute(out chan *Row, filterEmptyResults bool) {
 		pointCountInResult = 1
 	} else {
 		intervalTop := m.TMax/m.interval*m.interval + m.interval
-		pointCountInResult = int((intervalTop - m.TMin) / m.interval)
+		intervalBottom := m.TMin/m.interval*m.interval
+		pointCountInResult = int((intervalTop - intervalBottom) / m.interval)
 	}
 
 	if m.TMin == 0 && pointCountInResult > MaxGroupByPoints {
diff --git a/tx.go b/tx.go
index 0b1a8509b29..baca0dfe0cf 100644
--- a/tx.go
+++ b/tx.go
@@ -321,9 +321,13 @@ func (l *LocalMapper) NextInterval(interval int64) (interface{}, error) {
 		return nil, nil
 	}
 
+	intervalBottom := l.tmin
+
 	// Set the upper bound of the interval.
 	if interval > 0 {
-		l.tmax = l.tmin + interval - 1
+		// Make sure the bottom of the interval lands on a natural boundary.
+		intervalBottom = intervalBottom / interval * interval
+		l.tmax = intervalBottom + interval - 1
 	}
 
 	// Execute the map function. This local mapper acts as the iterator
@@ -339,7 +343,7 @@ func (l *LocalMapper) NextInterval(interval int64) (interface{}, error) {
 	}
 
 	// Move the interval forward.
-	l.tmin += interval
+	l.tmin = intervalBottom + interval
 
 	return val, nil
 }