diff --git a/sideband.c b/sideband.c
index 1c6bb0e25b..368647acf8 100644
--- a/sideband.c
+++ b/sideband.c
@@ -65,6 +65,8 @@ void list_config_color_sideband_slots(struct string_list *list, const char *pref
  * Optionally highlight one keyword in remote output if it appears at the start
  * of the line. This should be called for a single line only, which is
  * passed as the first N characters of the SRC array.
+ *
+ * NEEDSWORK: use "size_t n" instead for clarity.
  */
 static void maybe_colorize_sideband(struct strbuf *dest, const char *src, int n)
 {
@@ -75,7 +77,7 @@ static void maybe_colorize_sideband(struct strbuf *dest, const char *src, int n)
 		return;
 	}
 
-	while (isspace(*src)) {
+	while (0 < n && isspace(*src)) {
 		strbuf_addch(dest, *src);
 		src++;
 		n--;
@@ -84,6 +86,9 @@ static void maybe_colorize_sideband(struct strbuf *dest, const char *src, int n)
 	for (i = 0; i < ARRAY_SIZE(keywords); i++) {
 		struct keyword_entry *p = keywords + i;
 		int len = strlen(p->keyword);
+
+		if (n <= len)
+			continue;
 		/*
 		 * Match case insensitively, so we colorize output from existing
 		 * servers regardless of the case that they use for their
@@ -101,7 +106,6 @@ static void maybe_colorize_sideband(struct strbuf *dest, const char *src, int n)
 	}
 
 	strbuf_add(dest, src, n);
-
 }
 
 
diff --git a/t/t5409-colorize-remote-messages.sh b/t/t5409-colorize-remote-messages.sh
index eb1b8aa05d..f81b6813c0 100755
--- a/t/t5409-colorize-remote-messages.sh
+++ b/t/t5409-colorize-remote-messages.sh
@@ -15,6 +15,8 @@ test_expect_success 'setup' '
 	echo warning: warning
 	echo prefixerror: error
 	echo " " "error: leading space"
+	echo "    "
+	echo Err
 	exit 0
 	EOF
 	echo 1 >file &&
@@ -44,6 +46,12 @@ test_expect_success 'whole words at line start' '
 	grep "prefixerror: error" decoded
 '
 
+test_expect_success 'short line' '
+	git -C child -c color.remote=always push -f origin HEAD:short-line 2>output &&
+	test_decode_color <output >decoded &&
+	grep "remote: Err" decoded
+'
+
 test_expect_success 'case-insensitive' '
 	git --git-dir child/.git -c color.remote=always push -f origin HEAD:refs/heads/case-insensitive 2>output &&
 	cat output &&
@@ -58,6 +66,12 @@ test_expect_success 'leading space' '
 	grep "  <BOLD;RED>error<RESET>: leading space" decoded
 '
 
+test_expect_success 'spaces only' '
+	git -C child -c color.remote=always push -f origin HEAD:only-space 2>output &&
+	test_decode_color <output >decoded &&
+	grep "remote:     " decoded
+'
+
 test_expect_success 'no coloring for redirected output' '
 	git --git-dir child/.git push -f origin HEAD:refs/heads/redirected-output 2>output &&
 	test_decode_color <output >decoded &&