diff --git a/pretty.c b/pretty.c
index 31fc76b2f..af0f57ac8 100644
--- a/pretty.c
+++ b/pretty.c
@@ -586,7 +586,7 @@ static char *replace_encoding_header(char *buf, const char *encoding)
 	char *cp = buf;
 
 	/* guess if there is an encoding header before a \n\n */
-	while (strncmp(cp, "encoding ", strlen("encoding "))) {
+	while (!starts_with(cp, "encoding ")) {
 		cp = strchr(cp, '\n');
 		if (!cp || *++cp == '\n')
 			return buf;