diff --git a/core/collection/rollingwindow.go b/core/collection/rollingwindow.go
index 9f0db0a5..804fda3e 100644
--- a/core/collection/rollingwindow.go
+++ b/core/collection/rollingwindow.go
@@ -76,22 +76,23 @@ func (rw *RollingWindow) updateOffset() {
 	span := rw.span()
 	if span > 0 {
 		offset := rw.offset
-		// reset expired buckets
 		start := offset + 1
 		steps := start + span
-		offset = (offset + span) % rw.size
 		var remainder int
 		if steps > rw.size {
 			remainder = steps - rw.size
 			steps = rw.size
 		}
+
+		// reset expired buckets
 		for i := start; i < steps; i++ {
 			rw.win.resetBucket(i)
 		}
 		for i := 0; i < remainder; i++ {
 			rw.win.resetBucket(i)
 		}
-		rw.offset = offset
+
+		rw.offset = (offset + span) % rw.size
 		rw.lastTime = timex.Now()
 	}
 }
diff --git a/tools/goctl/Makefile b/tools/goctl/Makefile
index 8581c31d..b5808826 100644
--- a/tools/goctl/Makefile
+++ b/tools/goctl/Makefile
@@ -2,13 +2,13 @@ version := $(shell /bin/date "+%Y-%m-%d %H:%M")
 
 build:
 	go build -ldflags="-s -w" -ldflags="-X 'main.BuildTime=$(version)'" goctl.go
-	$(if $(shell command -v upx),upx goctl)
+	$(if $(shell command -v upx), upx goctl)
 mac:
 	GOOS=darwin go build -ldflags="-s -w" -ldflags="-X 'main.BuildTime=$(version)'" -o goctl-darwin goctl.go
-	$(if $(shell command -v upx),upx goctl-darwin)
+	$(if $(shell command -v upx), upx goctl-darwin)
 win:
 	GOOS=windows go build -ldflags="-s -w" -ldflags="-X 'main.BuildTime=$(version)'" -o goctl.exe goctl.go
-	$(if $(shell command -v upx),upx goctl.exe)
+	$(if $(shell command -v upx), upx goctl.exe)
 linux:
 	GOOS=linux go build -ldflags="-s -w" -ldflags="-X 'main.BuildTime=$(version)'" -o goctl-linux goctl.go
-	$(if $(shell command -v upx),upx goctl-linux)
+	$(if $(shell command -v upx), upx goctl-linux)