diff --git a/encoding/gsm7.go b/encoding/gsm7.go
index 50894cb..914dca7 100644
--- a/encoding/gsm7.go
+++ b/encoding/gsm7.go
@@ -15,6 +15,10 @@ func (c *GSM7Coder) Encode(s string, buf *bytes.Buffer) error {
 		bitshift    byte = 0
 		leap, shift bool
 	)
+	tbw := len(utf8) * 7 / 8
+	if buf.Available() < tbw {
+		buf.Grow(tbw)
+	}		
 
 	for index, septet := range utf8 {
 		if septet > 0b01111111 {
diff --git a/encoding/gsm7_test.go b/encoding/gsm7_test.go
index 2781079..298a26d 100644
--- a/encoding/gsm7_test.go
+++ b/encoding/gsm7_test.go
@@ -147,12 +147,12 @@ func TestGSM7DecodeSimpleASCIIString(t *testing.T) {
 
 // region insertat
 func TestInsertAtBeginning(t *testing.T) {
-    data := []byte{2, 3, 4, 0}
-    InsertAt(&data, 0, 1)
-    expected := []byte{1, 2, 3, 4}
-    if !bytes.Equal(data, expected) {
-        t.Errorf("expected %v, got %v", expected, data)
-    }
+	data := []byte{2, 3, 4, 0}
+	InsertAt(&data, 0, 1)
+	expected := []byte{1, 2, 3, 4}
+	if !bytes.Equal(data, expected) {
+		t.Errorf("expected %v, got %v", expected, data)
+	}
 }
 
 func TestInsertInMiddle(t *testing.T) {
@@ -174,13 +174,13 @@ func TestInsertAtEnd(t *testing.T) {
 }
 
 func TestIndexOutOfBounds(t *testing.T) {
-    data := []byte{2, 3, 4}
-    defer func() {
-        if r := recover(); r == nil {
-            t.Errorf("The code did not panic")
-        }
-    }()
-    InsertAt(&data, 4, 5)
+	data := []byte{2, 3, 4}
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("The code did not panic")
+		}
+	}()
+	InsertAt(&data, 4, 5)
 }
 
 func TestNegativeIndex(t *testing.T) {
@@ -194,12 +194,12 @@ func TestNegativeIndex(t *testing.T) {
 }
 
 func TestMaintainsOrderAfterInsertion(t *testing.T) {
-    data := []byte{2, 3, 4, 0}
-    InsertAt(&data, 1, 1)
-    expected := []byte{2, 1, 3, 4}
-    if !bytes.Equal(data, expected) {
-        t.Errorf("expected %v, got %v", expected, data)
-    }
+	data := []byte{2, 3, 4, 0}
+	InsertAt(&data, 1, 1)
+	expected := []byte{2, 1, 3, 4}
+	if !bytes.Equal(data, expected) {
+		t.Errorf("expected %v, got %v", expected, data)
+	}
 }
 
 func TestMaintainsLength(t *testing.T) {
@@ -251,4 +251,4 @@ func BenchmarkGSM7EncodeComplex8nASCIIString(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		coder.Encode(input, &buf)
 	}
-}
\ No newline at end of file
+}