diff --git a/decor/optimistic_string_writer.go b/decor/optimistic_string_writer.go
new file mode 100644
index 0000000..ea9fda7
--- /dev/null
+++ b/decor/optimistic_string_writer.go
@@ -0,0 +1,12 @@
+package decor
+
+import "io"
+
+func optimisticStringWriter(w io.Writer) func(string) {
+	return func(s string) {
+		_, err := io.WriteString(w, s)
+		if err != nil {
+			panic(err)
+		}
+	}
+}
diff --git a/decor/percentage.go b/decor/percentage.go
index 2b0a7a9..6e7f5c6 100644
--- a/decor/percentage.go
+++ b/decor/percentage.go
@@ -2,7 +2,6 @@
 
 import (
 	"fmt"
-	"io"
 	"strconv"
 
 	"github.com/vbauerster/mpb/v7/internal"
@@ -24,12 +23,12 @@
 		}
 	}
 
-	io.WriteString(st, strconv.FormatFloat(float64(s), 'f', prec, 64))
-
+	osw := optimisticStringWriter(st)
+	osw(strconv.FormatFloat(float64(s), 'f', prec, 64))
 	if st.Flag(' ') {
-		io.WriteString(st, " ")
+		osw(" ")
 	}
-	io.WriteString(st, "%")
+	osw("%")
 }
 
 // Percentage returns percentage decorator. It's a wrapper of NewPercentage.
diff --git a/decor/size_type.go b/decor/size_type.go
index 2b06255..12879b8 100644
--- a/decor/size_type.go
+++ b/decor/size_type.go
@@ -2,7 +2,6 @@
 
 import (
 	"fmt"
-	"io"
 	"strconv"
 )
 
@@ -50,12 +49,12 @@
 		unit = _iTiB
 	}
 
-	io.WriteString(st, strconv.FormatFloat(float64(self)/float64(unit), 'f', prec, 64))
-
+	osw := optimisticStringWriter(st)
+	osw(strconv.FormatFloat(float64(self)/float64(unit), 'f', prec, 64))
 	if st.Flag(' ') {
-		io.WriteString(st, " ")
+		osw(" ")
 	}
-	io.WriteString(st, unit.String())
+	osw(unit.String())
 }
 
 const (
@@ -99,10 +98,10 @@
 		unit = _TB
 	}
 
-	io.WriteString(st, strconv.FormatFloat(float64(self)/float64(unit), 'f', prec, 64))
-
+	osw := optimisticStringWriter(st)
+	osw(strconv.FormatFloat(float64(self)/float64(unit), 'f', prec, 64))
 	if st.Flag(' ') {
-		io.WriteString(st, " ")
+		osw(" ")
 	}
-	io.WriteString(st, unit.String())
+	osw(unit.String())
 }
diff --git a/decor/speed.go b/decor/speed.go
index 634edab..99cfde2 100644
--- a/decor/speed.go
+++ b/decor/speed.go
@@ -2,7 +2,6 @@
 
 import (
 	"fmt"
-	"io"
 	"math"
 	"time"
 
@@ -24,7 +23,7 @@
 
 func (self *speedFormatter) Format(st fmt.State, verb rune) {
 	self.Formatter.Format(st, verb)
-	io.WriteString(st, "/s")
+	optimisticStringWriter(st)("/s")
 }
 
 // EwmaSpeed exponential-weighted-moving-average based speed decorator.