diff --git a/fusl/src/string/wcsspn.c b/fusl/src/string/wcsspn.c
new file mode 100644
index 0000000..4320d8f
--- /dev/null
+++ b/fusl/src/string/wcsspn.c
@@ -0,0 +1,8 @@
+#include <wchar.h>
+
+size_t wcsspn(const wchar_t *s, const wchar_t *c)
+{
+	const wchar_t *a;
+	for (a=s; *s && wcschr(c, *s); s++);
+	return s-a;
+}