diff --git a/include/libdbc/dbc.hpp b/include/libdbc/dbc.hpp
index b732895..2dfe7bf 100644
--- a/include/libdbc/dbc.hpp
+++ b/include/libdbc/dbc.hpp
@@ -52,7 +52,7 @@ class DbcParser : public Parser {
 	void parse_dbc_nodes(std::istream& file_stream);
 	void parse_dbc_messages(const std::vector<std::string>& lines);
 
-	std::string get_extension(const std::string& file_name);
+	static std::string get_extension(const std::string& file_name);
 };
 
 }
diff --git a/src/dbc.cpp b/src/dbc.cpp
index 5c3e2c0..108ab7e 100644
--- a/src/dbc.cpp
+++ b/src/dbc.cpp
@@ -1,4 +1,5 @@
 #include <cstdint>
+#include <cstdio>
 #include <fstream>
 #include <istream>
 #include <libdbc/dbc.hpp>
@@ -93,7 +94,7 @@ void DbcParser::parse_file(const std::string& file) {
 }
 
 std::string DbcParser::get_extension(const std::string& file_name) {
-	size_t dot = file_name.find_last_of(".");
+	std::size_t dot = file_name.find_last_of(".");
 	if (dot != std::string::npos) {
 		return file_name.substr(dot, file_name.size() - dot);
 	}