diff --git a/collate/build/builder_test.go b/collate/build/builder_test.go
index ff0aba3a..0e022ecb 100644
--- a/collate/build/builder_test.go
+++ b/collate/build/builder_test.go
@@ -65,7 +65,7 @@ func newBuilder(t *testing.T, ducet []ducetElem) *Builder {
 			ces = append(ces, ce.w)
 		}
 		if err := b.Add([]rune(e.str), ces, nil); err != nil {
-			t.Errorf(err.Error())
+			t.Error(err)
 		}
 	}
 	b.t = &table{}
diff --git a/collate/build/trie_test.go b/collate/build/trie_test.go
index 4d4f6e4d..5109e091 100644
--- a/collate/build/trie_test.go
+++ b/collate/build/trie_test.go
@@ -29,7 +29,7 @@ func makeTestTrie(t *testing.T) trie {
 	idx.addTrie(n)
 	tr, err := idx.generate()
 	if err != nil {
-		t.Errorf(err.Error())
+		t.Error(err)
 	}
 	return *tr
 }
diff --git a/internal/cldrtree/generate.go b/internal/cldrtree/generate.go
index 0f0b5f3b..bdd77ce8 100644
--- a/internal/cldrtree/generate.go
+++ b/internal/cldrtree/generate.go
@@ -21,7 +21,7 @@ func generate(b *Builder, t *Tree, w *gen.CodeWriter) error {
 
 	fmt.Fprintf(w, "var tree = &cldrtree.Tree{locales, indices, buckets}\n\n")
 
-	w.WriteComment("Path values:\n" + b.stats())
+	w.WriteComment("Path values:\n%s", b.stats())
 	fmt.Fprintln(w)
 
 	// Generate enum types.
diff --git a/internal/gen/code.go b/internal/gen/code.go
index 75435c9b..fa4002b4 100644
--- a/internal/gen/code.go
+++ b/internal/gen/code.go
@@ -342,8 +342,7 @@ func (w *CodeWriter) writeSlice(x interface{}, isArray bool) {
 			if !reflect.DeepEqual(zero, x) {
 				line := fmt.Sprintf("%#v,\n", x)
 				line = line[strings.IndexByte(line, '{'):]
-				w.printf("%d: ", i)
-				w.printf(line)
+				w.printf("%d: %s", i, line)
 			}
 		}
 	case reflect.Array: