diff --git a/svg01.h b/svg01.h
index 5e3353c..1a70440 100644
--- a/svg01.h
+++ b/svg01.h
@@ -1,5 +1,6 @@
 #pragma once
+#include <string>
 #include <vector>
 
 void
-show_histogram_svg(const std::vector<size_t>& bins);
+show_histogram_svg(const std::vector<size_t>& bins, std::string stroke, std::string fill);