diff --git a/filesystem.go b/filesystem.go
index 40975c0..4717ee8 100644
--- a/filesystem.go
+++ b/filesystem.go
@@ -33,7 +33,7 @@ func init() {
 	}
 }
 
-var noOutToIn = fmt.Errorf("no output to input source")
+var errNoOutToIn = fmt.Errorf("no output to input source")
 
 // Walk the specified pathnames, collecting regular files.
 func getFilenames(pathnames []string, outFilename string) []string {
@@ -55,7 +55,7 @@ func getFilenames(pathnames []string, outFilename string) []string {
 			return err
 		}
 		if absolute == absOutFile {
-			return noOutToIn
+			return errNoOutToIn
 		}
 		relative, _ := filepath.Rel(workingDir, absolute) // Failure is okay.
 		if relative != "" {
@@ -77,7 +77,7 @@ func getFilenames(pathnames []string, outFilename string) []string {
 			log.Print("warning: path -: Reading from standard input is unsupported.")
 			continue
 		} else if err := filepath.Walk(pathname, fileWalker); err != nil {
-			if err == noOutToIn {
+			if err == errNoOutToIn {
 				log.Fatalf("error: path %s: Output file cannot be an input source.", pathname)
 			} else {
 				log.Printf("warning: path %s: %s", pathname, err.Error())
diff --git a/sort.go b/sort.go
index 60c0881..b947443 100644
--- a/sort.go
+++ b/sort.go
@@ -10,6 +10,7 @@ import (
 	"unicode"
 )
 
+// StringsInsensitively provides for case insensitively sorting slices of strings.
 type StringsInsensitively []string
 
 func (p StringsInsensitively) Len() int {