diff --git a/Documentation/technical/api-strbuf.txt b/Documentation/technical/api-strbuf.txt
index 4396be9dda..50690186d3 100644
--- a/Documentation/technical/api-strbuf.txt
+++ b/Documentation/technical/api-strbuf.txt
@@ -134,6 +134,10 @@ Functions
 
 	Strip whitespace from the beginning of a string.
 
+`strbuf_tolower`::
+
+	Lowercase each character in the buffer using `tolower`.
+
 `strbuf_cmp`::
 
 	Compare two buffers. Returns an integer less than, equal to, or greater
diff --git a/config.c b/config.c
index 3c3e31448e..9319aa12f3 100644
--- a/config.c
+++ b/config.c
@@ -147,12 +147,6 @@ int git_config_include(const char *var, const char *value, void *data)
 	return ret;
 }
 
-static void lowercase(char *p)
-{
-	for (; *p; p++)
-		*p = tolower(*p);
-}
-
 void git_config_push_parameter(const char *text)
 {
 	struct strbuf env = STRBUF_INIT;
@@ -180,7 +174,7 @@ int git_config_parse_parameter(const char *text,
 		strbuf_list_free(pair);
 		return error("bogus config parameter: %s", text);
 	}
-	lowercase(pair[0]->buf);
+	strbuf_tolower(pair[0]);
 	if (fn(pair[0]->buf, pair[1] ? pair[1]->buf : NULL, data) < 0) {
 		strbuf_list_free(pair);
 		return -1;
diff --git a/strbuf.c b/strbuf.c
index f5d609a51f..c8217755e5 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -99,6 +99,13 @@ void strbuf_ltrim(struct strbuf *sb)
 	sb->buf[sb->len] = '\0';
 }
 
+void strbuf_tolower(struct strbuf *sb)
+{
+	char *p = sb->buf, *end = sb->buf + sb->len;
+	for (; p < end; p++)
+		*p = tolower(*p);
+}
+
 struct strbuf **strbuf_split_buf(const char *str, size_t slen,
 				 int terminator, int max)
 {
diff --git a/strbuf.h b/strbuf.h
index 4de7531c43..25328b9e81 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -45,6 +45,7 @@ static inline void strbuf_setlen(struct strbuf *sb, size_t len)
 extern void strbuf_trim(struct strbuf *);
 extern void strbuf_rtrim(struct strbuf *);
 extern void strbuf_ltrim(struct strbuf *);
+extern void strbuf_tolower(struct strbuf *sb);
 extern int strbuf_cmp(const struct strbuf *, const struct strbuf *);
 
 /*