diff --git a/src/config/Parser.cxx b/src/config/Parser.cxx
index 89c3458c1..9bfb735c2 100644
--- a/src/config/Parser.cxx
+++ b/src/config/Parser.cxx
@@ -70,28 +70,28 @@ ParsePositive(const char *s)
 	return (unsigned)value;
 }
 
-template<size_t OPERAND>
-static size_t
-Multiply(size_t value)
+template<std::size_t OPERAND>
+static std::size_t
+Multiply(std::size_t value)
 {
-	static constexpr size_t MAX_VALUE = SIZE_MAX / OPERAND;
+	static constexpr std::size_t MAX_VALUE = SIZE_MAX / OPERAND;
 	if (value > MAX_VALUE)
 		throw std::runtime_error("Value too large");
 
 	return value * OPERAND;
 }
 
-size_t
-ParseSize(const char *s, size_t default_factor)
+std::size_t
+ParseSize(const char *s, std::size_t default_factor)
 {
 	char *endptr;
-	size_t value = strtoul(s, &endptr, 10);
+	std::size_t value = strtoul(s, &endptr, 10);
 	if (endptr == s)
 		throw std::runtime_error("Failed to parse integer");
 
-	static constexpr size_t KILO = 1024;
-	static constexpr size_t MEGA = 1024 * KILO;
-	static constexpr size_t GIGA = 1024 * MEGA;
+	static constexpr std::size_t KILO = 1024;
+	static constexpr std::size_t MEGA = 1024 * KILO;
+	static constexpr std::size_t GIGA = 1024 * MEGA;
 
 	s = StripLeft(endptr);
 
diff --git a/src/config/Parser.hxx b/src/config/Parser.hxx
index b448709cd..71feec4ca 100644
--- a/src/config/Parser.hxx
+++ b/src/config/Parser.hxx
@@ -51,7 +51,7 @@ ParsePositive(const char *s);
  *
  * Throws on error.
  */
-size_t
-ParseSize(const char *s, size_t default_factor=1);
+std::size_t
+ParseSize(const char *s, std::size_t default_factor=1);
 
 #endif