diff --git a/src/string_util.cpp b/src/string_util.cpp
index 23804253c..ce7e2bba2 100644
--- a/src/string_util.cpp
+++ b/src/string_util.cpp
@@ -81,8 +81,7 @@ namespace libtorrent {
 
 	bool is_space(char c)
 	{
-		static const char* ws = " \t\n\r\f\v";
-		return strchr(ws, c) != nullptr;
+		return c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\f' || c == '\v';
 	}
 
 	char to_lower(char c)
diff --git a/test/test_string.cpp b/test/test_string.cpp
index 95caddf52..ae8f10704 100644
--- a/test/test_string.cpp
+++ b/test/test_string.cpp
@@ -91,6 +91,8 @@ TORRENT_TEST(is_space)
 	TEST_CHECK(is_space('\t'));
 	TEST_CHECK(is_space('\n'));
 	TEST_CHECK(is_space('\r'));
+	TEST_CHECK(is_space('\f'));
+	TEST_CHECK(is_space('\v'));
 }
 
 TORRENT_TEST(to_lower)