diff --git a/src/io/FileReader.hxx b/src/io/FileReader.hxx
index 476ccea7d..431f9afa2 100644
--- a/src/io/FileReader.hxx
+++ b/src/io/FileReader.hxx
@@ -67,7 +67,7 @@ public:
 	FileInfo GetFileInfo() const;
 
 	[[gnu::pure]]
-	uint64_t GetSize() const noexcept {
+	uint_least64_t GetSize() const noexcept {
 #ifdef _WIN32
 		LARGE_INTEGER size;
 		return GetFileSizeEx(handle, &size)
@@ -79,7 +79,7 @@ public:
 	}
 
 	[[gnu::pure]]
-	uint64_t GetPosition() const noexcept {
+	uint_least64_t GetPosition() const noexcept {
 #ifdef _WIN32
 		LARGE_INTEGER zero;
 		zero.QuadPart = 0;