diff --git a/src/sed/fast_io.rs b/src/sed/fast_io.rs
index 5ea8bf3d..838965e4 100644
--- a/src/sed/fast_io.rs
+++ b/src/sed/fast_io.rs
@@ -678,6 +678,15 @@ impl OutputBuffer {
         )))
     }
 
+    /// Schedule the specified text for output unchanged, after any
+    /// deferred newline.
+    pub fn write_raw(&mut self, bytes: &[u8]) -> io::Result<()> {
+        self.flush_pending_newline()?;
+        #[cfg(unix)]
+        self.flush_mmap(WriteRange::Complete)?;
+        self.out.write_all(bytes)
+    }
+
     /// Copy the specified file to the output.
     pub fn copy_file(&mut self, path: &PathBuf) -> io::Result<()> {
         // Flush mmap writes, if any.
diff --git a/src/sed/processor.rs b/src/sed/processor.rs
index 3f0ebb8b..948b3ed2 100644
--- a/src/sed/processor.rs
+++ b/src/sed/processor.rs
@@ -467,7 +467,7 @@ fn flush_appends(output: &mut OutputBuffer, context: &mut ProcessingContext) ->
     for elem in &context.append_elements {
         match elem {
             AppendElement::Text(text) => {
-                output.write_bytes(text.as_ref())?;
+                output.write_raw(text.as_ref())?;
             }
             AppendElement::Path(path) => {
                 output.copy_file(path)?;
@@ -567,9 +567,7 @@ fn list(
 ) -> UResult<()> {
     // Special case for an empty pattern space
     if line.is_empty() {
-        if line.is_newline_terminated() {
-            output.write_str("$\n")?;
-        }
+        output.write_str("$\n")?;
         return Ok(());
     }
 
@@ -737,7 +735,7 @@ fn process_file(
                     }
                     CommandData::Text(cmd_bytes) => {
                         let shell_out = shell_stdout(cmd_bytes.to_vec(), &command, context)?;
-                        output.write_bytes(&shell_out)?;
+                        output.write_raw(&shell_out)?;
                     }
                     _ => panic!("invalid 'e' command data"),
                 },
diff --git a/tests/by-util/test_sed.rs b/tests/by-util/test_sed.rs
index add24b83..62a90f1c 100644
--- a/tests/by-util/test_sed.rs
+++ b/tests/by-util/test_sed.rs
@@ -3090,3 +3090,45 @@ fn test_posix_reject_flags() {
         .code_is(1)
         .stderr_is("sed: <script argument 1>:1:7: error: unknown option to 's'\n");
 }
+
+/// `R` copies a line lacking a newline unchanged, as GNU sed does.
+#[test]
+fn read_one_line_without_newline_is_copied_unchanged() -> std::io::Result<()> {
+    let temp = NamedTempFile::new()?;
+    fs::write(temp.path(), "x")?;
+    new_ucmd!()
+        .arg(format!("R {}", temp.path().display()))
+        .pipe_in("a\nb\n")
+        .succeeds()
+        .stdout_is("a\nxb\n");
+    Ok(())
+}
+
+/// The output of the `e` command is copied unchanged, as GNU sed does.
+#[cfg(unix)]
+#[test]
+fn execute_command_output_is_copied_unchanged() {
+    new_ucmd!()
+        .arg("1e printf hi")
+        .pipe_in("a\nb\n")
+        .succeeds()
+        .stdout_is("hia\nb\n");
+    // A line that lacks its newline is ended before the output, even when
+    // there is none.
+    new_ucmd!()
+        .args(&["-n", "p;e true"])
+        .pipe_in("a")
+        .succeeds()
+        .stdout_is("a\n");
+}
+
+/// `l` shows an empty pattern space as `$`, even when the line lacked a
+/// newline, as GNU sed does.
+#[test]
+fn list_empty_line_without_newline() {
+    new_ucmd!()
+        .args(&["-n", "s/a//;l"])
+        .pipe_in("a")
+        .succeeds()
+        .stdout_is("$\n");
+}