diff --git a/include/fmt/os.h b/include/fmt/os.h
index 78971e37..680ada4c 100644
--- a/include/fmt/os.h
+++ b/include/fmt/os.h
@@ -291,7 +291,8 @@ class file {
 
   file(file&& other) FMT_NOEXCEPT : fd_(other.fd_) { other.fd_ = -1; }
 
-  file& operator=(file&& other) FMT_NOEXCEPT {
+  // Move assignment is not noexcept because close may throw.
+  file& operator=(file&& other) {
     close();
     fd_ = other.fd_;
     other.fd_ = -1;
@@ -399,7 +400,6 @@ class ostream final : private detail::buffer<char> {
     other.clear();
     other.set(nullptr, 0);
   }
-
   ~ostream() {
     flush();
     delete[] data();