diff --git a/src/lib/curl/Request.cxx b/src/lib/curl/Request.cxx
index 45dd440ec..9a287503f 100644
--- a/src/lib/curl/Request.cxx
+++ b/src/lib/curl/Request.cxx
@@ -224,8 +224,8 @@ CurlRequest::HeaderFunction(StringView s) noexcept
 	headers.emplace(std::move(name), std::string(value, end));
 }
 
-size_t
-CurlRequest::_HeaderFunction(char *ptr, size_t size, size_t nmemb,
+std::size_t
+CurlRequest::_HeaderFunction(char *ptr, std::size_t size, std::size_t nmemb,
 			     void *stream) noexcept
 {
 	CurlRequest &c = *(CurlRequest *)stream;
@@ -236,8 +236,8 @@ CurlRequest::_HeaderFunction(char *ptr, size_t size, size_t nmemb,
 	return size;
 }
 
-inline size_t
-CurlRequest::DataReceived(const void *ptr, size_t received_size) noexcept
+inline std::size_t
+CurlRequest::DataReceived(const void *ptr, std::size_t received_size) noexcept
 {
 	assert(received_size > 0);
 
@@ -251,8 +251,8 @@ CurlRequest::DataReceived(const void *ptr, size_t received_size) noexcept
 
 }
 
-size_t
-CurlRequest::WriteFunction(char *ptr, size_t size, size_t nmemb,
+std::size_t
+CurlRequest::WriteFunction(char *ptr, std::size_t size, std::size_t nmemb,
 			   void *stream) noexcept
 {
 	CurlRequest &c = *(CurlRequest *)stream;
diff --git a/src/lib/curl/Request.hxx b/src/lib/curl/Request.hxx
index a43b29bf9..67785b1df 100644
--- a/src/lib/curl/Request.hxx
+++ b/src/lib/curl/Request.hxx
@@ -165,17 +165,17 @@ private:
 	void FinishHeaders();
 	void FinishBody();
 
-	size_t DataReceived(const void *ptr, size_t size) noexcept;
+	std::size_t DataReceived(const void *ptr, std::size_t size) noexcept;
 
 	void HeaderFunction(StringView s) noexcept;
 
 	/** called by curl when new data is available */
-	static size_t _HeaderFunction(char *ptr, size_t size, size_t nmemb,
-				      void *stream) noexcept;
+	static std::size_t _HeaderFunction(char *ptr, std::size_t size, std::size_t nmemb,
+					   void *stream) noexcept;
 
 	/** called by curl when new data is available */
-	static size_t WriteFunction(char *ptr, size_t size, size_t nmemb,
-				    void *stream) noexcept;
+	static std::size_t WriteFunction(char *ptr, std::size_t size, std::size_t nmemb,
+					 void *stream) noexcept;
 };
 
 #endif