diff --git a/src/builtin_read.cpp b/src/builtin_read.cpp
index 4c7895882..fe4b842ae 100644
--- a/src/builtin_read.cpp
+++ b/src/builtin_read.cpp
@@ -202,7 +202,6 @@ static int read_interactive(wcstring &buff, int nchars, bool shell, bool silent,
                             const wchar_t *prompt, const wchar_t *right_prompt,
                             const wchar_t *commandline) {
     int exit_res = STATUS_CMD_OK;
-    const wchar_t *line;
 
     // TODO: rationalize this.
     const auto &vars = env_stack_t::principal();
@@ -227,17 +226,16 @@ static int read_interactive(wcstring &buff, int nchars, bool shell, bool silent,
     proc_push_interactive(1);
 
     event_fire_generic(L"fish_prompt");
-    line = reader_readline(nchars);
+    auto mline = reader_readline(nchars);
     proc_pop_interactive();
-    if (line) {
-        if (0 < nchars && (size_t)nchars < wcslen(line)) {
+    if (mline) {
+        buff = mline.acquire();
+        if (nchars > 0 && (size_t)nchars < buff.size()) {
             // Line may be longer than nchars if a keybinding used `commandline -i`
             // note: we're deliberately throwing away the tail of the commandline.
             // It shouldn't be unread because it was produced with `commandline -i`,
             // not typed.
-            buff = wcstring(line, nchars);
-        } else {
-            buff = wcstring(line);
+            buff.resize(nchars);
         }
     } else {
         exit_res = STATUS_CMD_ERROR;
diff --git a/src/reader.cpp b/src/reader.cpp
index 8308943ec..a370e2719 100644
--- a/src/reader.cpp
+++ b/src/reader.cpp
@@ -2373,12 +2373,12 @@ static int read_i() {
 
         // Put buff in temporary string and clear buff, so that we can handle a call to
         // reader_set_buffer during evaluation.
-        const wchar_t *tmp = reader_readline(0);
+        maybe_t<wcstring> tmp = reader_readline(0);
 
         if (shell_is_exiting()) {
             handle_end_loop();
         } else if (tmp) {
-            const wcstring command = tmp;
+            const wcstring command = tmp.acquire();
             update_buff_pos(&data->command_line, 0);
             data->command_line.text.clear();
             data->command_line_changed(&data->command_line);
@@ -2448,7 +2448,7 @@ static bool text_ends_in_comment(const wcstring &text) {
     return token.type == TOK_COMMENT;
 }
 
-const wchar_t *reader_readline(int nchars) {
+maybe_t<wcstring> reader_readline(int nchars) {
     wint_t c;
     int last_char = 0;
     size_t yank_len = 0;
@@ -3350,7 +3350,7 @@ const wchar_t *reader_readline(int nchars) {
         outputter_t::stdoutput().set_color(rgb_color_t::reset(), rgb_color_t::reset());
     }
 
-    return finished ? data->command_line.text.c_str() : NULL;
+    return finished ? maybe_t<wcstring>{data->command_line.text} : none();
 }
 
 bool jump(jump_direction_t dir, jump_precision_t precision, editable_line_t *el, wchar_t target) {
diff --git a/src/reader.h b/src/reader.h
index 0c28109b2..871547cfd 100644
--- a/src/reader.h
+++ b/src/reader.h
@@ -144,7 +144,7 @@ bool reader_thread_job_is_stale();
 /// characters even if a full line has not yet been read. Note: the returned value may be longer
 /// than nchars if a single keypress resulted in multiple characters being inserted into the
 /// commandline.
-const wchar_t *reader_readline(int nchars);
+maybe_t<wcstring> reader_readline(int nchars);
 
 /// Push a new reader environment.
 void reader_push(const wcstring &name);