diff --git a/attribute/generated.go b/attribute/generated.go
index 892284a..9b5b083 100644
--- a/attribute/generated.go
+++ b/attribute/generated.go
@@ -19,7 +19,7 @@ func Accept(value ...string) hatmill.Attrib {
 func AcceptCharset(value ...string) hatmill.Attrib {
 	return hatmill.Attrib{
 		Key:   "accept-charset",
-		Value: String(strings.Join(value, " ")),
+		Value: String(SpaceList(value).String()),
 	}
 }
 
@@ -103,7 +103,7 @@ func Cite(value string) hatmill.Attrib {
 func Class(value ...string) hatmill.Attrib {
 	return hatmill.Attrib{
 		Key:   "class",
-		Value: String(strings.Join(value, " ")),
+		Value: String(SpaceList(value).String()),
 	}
 }
 
@@ -243,7 +243,7 @@ func Enctype(value string) hatmill.Attrib {
 func For(value ...string) hatmill.Attrib {
 	return hatmill.Attrib{
 		Key:   "for",
-		Value: String(strings.Join(value, " ")),
+		Value: String(SpaceList(value).String()),
 	}
 }
 
@@ -275,7 +275,7 @@ func Formmethod(value string) hatmill.Attrib {
 func Headers(value ...string) hatmill.Attrib {
 	return hatmill.Attrib{
 		Key:   "headers",
-		Value: String(strings.Join(value, " ")),
+		Value: String(SpaceList(value).String()),
 	}
 }
 
@@ -500,7 +500,7 @@ func Pattern(value string) hatmill.Attrib {
 func Ping(value ...string) hatmill.Attrib {
 	return hatmill.Attrib{
 		Key:   "ping",
-		Value: String(strings.Join(value, " ")),
+		Value: String(SpaceList(value).String()),
 	}
 }
 
@@ -547,7 +547,7 @@ func Referrerpolicy(value string) hatmill.Attrib {
 func Rel(value ...string) hatmill.Attrib {
 	return hatmill.Attrib{
 		Key:   "rel",
-		Value: String(strings.Join(value, " ")),
+		Value: String(SpaceList(value).String()),
 	}
 }
 
@@ -585,7 +585,7 @@ func Rowspan(value int) hatmill.Attrib {
 func Sandbox(value ...string) hatmill.Attrib {
 	return hatmill.Attrib{
 		Key:   "sandbox",
-		Value: String(strings.Join(value, " ")),
+		Value: String(SpaceList(value).String()),
 	}
 }
 
diff --git a/attribute/generated_test.go b/attribute/generated_test.go
index bf7b096..34b06fc 100644
--- a/attribute/generated_test.go
+++ b/attribute/generated_test.go
@@ -14,15 +14,6 @@ func testAttribValue(t *testing.T, attrib hatmill.Attrib, expectedValue string)
 	}
 }
 
-func TestSpaceList(t *testing.T) {
-	t.Run("empty", func(t *testing.T) {
-		testAttribValue(t, attribute.Class(), "")
-	})
-	t.Run("nonempty", func(t *testing.T) {
-		testAttribValue(t, attribute.Class("alpha", "bravo", "charlie"), "alpha bravo charlie")
-	})
-}
-
 func TestCommaList(t *testing.T) {
 	t.Run("empty", func(t *testing.T) {
 		testAttribValue(t, attribute.Class(), "")
diff --git a/attribute/value_types.go b/attribute/value_types.go
new file mode 100644
index 0000000..761f331
--- /dev/null
+++ b/attribute/value_types.go
@@ -0,0 +1,9 @@
+package attribute
+
+import "strings"
+
+type SpaceList []string
+
+func (l SpaceList) String() string {
+	return strings.Join(l, " ")
+}
diff --git a/attribute/value_types_test.go b/attribute/value_types_test.go
new file mode 100644
index 0000000..cef5d75
--- /dev/null
+++ b/attribute/value_types_test.go
@@ -0,0 +1,24 @@
+package attribute_test
+
+import (
+	"gitlab.codemonkeysoftware.net/b/hatmill/attribute"
+	"testing"
+)
+
+func expectEqualStrings(t *testing.T, actual, expected string) {
+	if actual != expected {
+		t.Fatalf("expected %q, got %q", expected, actual)
+	}
+}
+
+func TestSpaceList(t *testing.T) {
+	t.Run("empty", func(t *testing.T) {
+		expectEqualStrings(t, attribute.SpaceList{}.String(), "")
+	})
+
+	t.Run("nonempty", func(t *testing.T) {
+		expected := "alpha bravo charlie"
+		actual := attribute.SpaceList{"alpha", "bravo", "charlie"}.String()
+		expectEqualStrings(t, actual, expected)
+	})
+}
diff --git a/internal/codegen/codegen.go b/internal/codegen/codegen.go
index 80081f7..3db45dd 100644
--- a/internal/codegen/codegen.go
+++ b/internal/codegen/codegen.go
@@ -68,8 +68,7 @@ var attribTypes = map[string]AttribTypeInfo{
 		Imports:  []string{"strconv"},
 	},
 	"space list": {
-		Template: listTemplate(" "),
-		Imports:  []string{"strings"},
+		Template: simpleTemplate("...string", "SpaceList(%s).String()"),
 	},
 	"comma list": {
 		Template: listTemplate(","),