diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index 654ccc3d..252154c6 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -1517,6 +1517,12 @@ template <typename F> class apple_file : public file_base<F> {
     this->file_->_p += size;
     this->file_->_w -= size;
   }
+
+  bool needs_flush() const {
+    if ((this->file_->_flags & 1) == 0) return false;  // 1 is __SLBF.
+    return memchr(this->file_->_p + this->file_->_w, '\n',
+                  to_unsigned(-this->file_->_w));
+  }
 };
 
 // A fallback FILE wrapper.
@@ -1529,6 +1535,7 @@ template <typename F> class fallback_file : public file_base<F> {
   using file_base<F>::file_base;
 
   auto is_buffered() const -> bool { return false; }
+  auto needs_flush() const -> bool { return false; }
 
   auto get_read_buffer() const -> span<const char> {
     return {&next_, has_next_ ? 1u : 0u};
@@ -1581,7 +1588,9 @@ class file_print_buffer : public buffer<char> {
   }
   ~file_print_buffer() {
     file_.advance_write_buffer(size());
+    bool flush = file_.needs_flush();
     funlockfile(file_);
+    if (flush) fflush(file_);
   }
 };
 
diff --git a/test/format-test.cc b/test/format-test.cc
index 2b8255a5..9c89e898 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1752,6 +1752,21 @@ TEST(format_test, big_print) {
   EXPECT_WRITE(stdout, big_print(), std::string(count, 'x'));
 }
 
+// Windows CRT implements _IOLBF incorrectly (full buffering).
+#if FMT_USE_FCNTL && !defined(_WIN32)
+TEST(format_test, line_buffering) {
+  auto pipe = fmt::pipe();
+  auto read_end = pipe.read_end.fdopen("r");
+  auto write_end = pipe.write_end.fdopen("w");
+  setvbuf(write_end.get(), nullptr, _IOLBF, 4096);
+  write_end.print("42\n");
+  int n = 0;
+  int result = fscanf(read_end.get(), "%d", &n);
+  (void)result;
+  EXPECT_EQ(n, 42);
+}
+#endif
+
 TEST(format_test, variadic) {
   EXPECT_EQ(fmt::format("{}c{}", "ab", 1), "abc1");
 }