diff --git a/decor/speed.go b/decor/speed.go
index 39b4691..f743766 100644
--- a/decor/speed.go
+++ b/decor/speed.go
@@ -22,8 +22,8 @@
 // Note that it's necessary to supply bar.Incr* methods with incremental
 // work duration as second argument, in order for this decorator to
 // work correctly. This decorator is a wrapper of MovingAverageSpeed.
-func EwmaSpeed(unit int, fmt string, age float64, wcc ...WC) Decorator {
-	return MovingAverageSpeed(unit, fmt, ewma.NewMovingAverage(age), wcc...)
+func EwmaSpeed(unit int, format string, age float64, wcc ...WC) Decorator {
+	return MovingAverageSpeed(unit, format, ewma.NewMovingAverage(age), wcc...)
 }
 
 // MovingAverageSpeed decorator relies on MovingAverage implementation
@@ -31,41 +31,52 @@
 //
 //	`unit` one of [0|UnitKiB|UnitKB] zero for no unit
 //
-//	`fmt` printf compatible verb for value, like "%f" or "%d"
+//	`format` printf compatible verb for value, like "%f" or "%d"
 //
 //	`average` MovingAverage implementation
 //
 //	`wcc` optional WC config
 //
-// fmt examples:
+// format examples:
 //
-//	unit=UnitKiB, fmt="%.1f"  output: "1.0MiB/s"
-//	unit=UnitKiB, fmt="% .1f" output: "1.0 MiB/s"
-//	unit=UnitKB,  fmt="%.1f"  output: "1.0MB/s"
-//	unit=UnitKB,  fmt="% .1f" output: "1.0 MB/s"
+//	unit=UnitKiB, format="%.1f"  output: "1.0MiB/s"
+//	unit=UnitKiB, format="% .1f" output: "1.0 MiB/s"
+//	unit=UnitKB,  format="%.1f"  output: "1.0MB/s"
+//	unit=UnitKB,  format="% .1f" output: "1.0 MB/s"
 //
-func MovingAverageSpeed(unit int, fmt string, average MovingAverage, wcc ...WC) Decorator {
+func MovingAverageSpeed(unit int, format string, average MovingAverage, wcc ...WC) Decorator {
 	var wc WC
 	for _, widthConf := range wcc {
 		wc = widthConf
 	}
+	if format == "" {
+		format = "%.0f"
+	}
 	wc.Init()
-	if fmt == "" {
-		fmt = "%.0f"
-	}
 	d := &movingAverageSpeed{
 		WC:      wc,
-		unit:    unit,
-		fmt:     fmt,
 		average: average,
+	}
+	switch unit {
+	case UnitKiB:
+		d.producer = func(speed float64) string {
+			return fmt.Sprintf(format, &speedType{SizeB1024(math.Round(speed))})
+		}
+	case UnitKB:
+		d.producer = func(speed float64) string {
+			return fmt.Sprintf(format, &speedType{SizeB1000(math.Round(speed))})
+		}
+	default:
+		d.producer = func(speed float64) string {
+			return fmt.Sprintf(format, speed)
+		}
 	}
 	return d
 }
 
 type movingAverageSpeed struct {
 	WC
-	unit        int
-	fmt         string
+	producer    func(float64) string
 	average     ewma.MovingAverage
 	msg         string
 	completeMsg *string
@@ -79,18 +90,7 @@
 		return d.FormatMsg(d.msg)
 	}
 
-	speed := d.average.Value()
-
-	var val interface{}
-	switch d.unit {
-	case UnitKiB:
-		val = &speedType{SizeB1024(math.Round(speed))}
-	case UnitKB:
-		val = &speedType{SizeB1000(math.Round(speed))}
-	default:
-		val = speed
-	}
-	d.msg = fmt.Sprintf(d.fmt, val)
+	d.msg = d.producer(d.average.Value())
 
 	return d.FormatMsg(d.msg)
 }
@@ -113,8 +113,8 @@
 
 // AverageSpeed decorator with dynamic unit measure adjustment. It's
 // a wrapper of NewAverageSpeed.
-func AverageSpeed(unit int, fmt string, wcc ...WC) Decorator {
-	return NewAverageSpeed(unit, fmt, time.Now(), wcc...)
+func AverageSpeed(unit int, format string, wcc ...WC) Decorator {
+	return NewAverageSpeed(unit, format, time.Now(), wcc...)
 }
 
 // NewAverageSpeed decorator with dynamic unit measure adjustment and
@@ -122,42 +122,53 @@
 //
 //	`unit` one of [0|UnitKiB|UnitKB] zero for no unit
 //
-//	`fmt` printf compatible verb for value, like "%f" or "%d"
+//	`format` printf compatible verb for value, like "%f" or "%d"
 //
 //	`startTime` start time
 //
 //	`wcc` optional WC config
 //
-// fmt examples:
+// format examples:
 //
-//	unit=UnitKiB, fmt="%.1f"  output: "1.0MiB/s"
-//	unit=UnitKiB, fmt="% .1f" output: "1.0 MiB/s"
-//	unit=UnitKB,  fmt="%.1f"  output: "1.0MB/s"
-//	unit=UnitKB,  fmt="% .1f" output: "1.0 MB/s"
+//	unit=UnitKiB, format="%.1f"  output: "1.0MiB/s"
+//	unit=UnitKiB, format="% .1f" output: "1.0 MiB/s"
+//	unit=UnitKB,  format="%.1f"  output: "1.0MB/s"
+//	unit=UnitKB,  format="% .1f" output: "1.0 MB/s"
 //
-func NewAverageSpeed(unit int, fmt string, startTime time.Time, wcc ...WC) Decorator {
+func NewAverageSpeed(unit int, format string, startTime time.Time, wcc ...WC) Decorator {
 	var wc WC
 	for _, widthConf := range wcc {
 		wc = widthConf
 	}
+	if format == "" {
+		format = "%.0f"
+	}
 	wc.Init()
-	if fmt == "" {
-		fmt = "%.0f"
-	}
 	d := &averageSpeed{
 		WC:        wc,
-		unit:      unit,
 		startTime: startTime,
-		fmt:       fmt,
+	}
+	switch unit {
+	case UnitKiB:
+		d.producer = func(speed float64) string {
+			return fmt.Sprintf(format, &speedType{SizeB1024(math.Round(speed))})
+		}
+	case UnitKB:
+		d.producer = func(speed float64) string {
+			return fmt.Sprintf(format, &speedType{SizeB1000(math.Round(speed))})
+		}
+	default:
+		d.producer = func(speed float64) string {
+			return fmt.Sprintf(format, speed)
+		}
 	}
 	return d
 }
 
 type averageSpeed struct {
 	WC
-	unit        int
 	startTime   time.Time
-	fmt         string
+	producer    func(float64) string
 	msg         string
 	completeMsg *string
 }
@@ -170,19 +181,8 @@
 		return d.FormatMsg(d.msg)
 	}
 
-	timeElapsed := time.Since(d.startTime)
-	speed := float64(st.Current) / timeElapsed.Seconds()
-
-	var val interface{}
-	switch d.unit {
-	case UnitKiB:
-		val = &speedType{SizeB1024(math.Round(speed))}
-	case UnitKB:
-		val = &speedType{SizeB1000(math.Round(speed))}
-	default:
-		val = speed
-	}
-	d.msg = fmt.Sprintf(d.fmt, val)
+	speed := float64(st.Current) / time.Since(d.startTime).Seconds()
+	d.msg = d.producer(speed)
 
 	return d.FormatMsg(d.msg)
 }