diff --git a/sys/include/shell.h b/sys/include/shell.h
index 513ab64e6b..d33eb9fe18 100644
--- a/sys/include/shell.h
+++ b/sys/include/shell.h
@@ -270,6 +270,31 @@ int shell_handle_input_line(const shell_command_t *commands, char *line);
 int shell_parse_file(const shell_command_t *commands,
                      const char *filename, unsigned *line_nr);
 
+/**
+ * @brief   Read a single line from standard input into a buffer.
+ *
+ * In addition to copying characters, this routine echoes the line back to
+ * stdout and also supports primitive line editing.
+ *
+ * If the input line is too long, the input will still be consumed until the end
+ * to prevent the next line from containing garbage.
+ *
+ * We allow Unix (`\n`), DOS (`\r\n`), and Mac linebreaks (`\r`).
+ * QEMU transmits only a single `\r` == 13 on hitting enter ("-serial stdio").
+ * DOS newlines are handled like hitting enter twice.
+ *
+ * @param   buf     Buffer where the input will be placed.
+ * @param   size    Size of the buffer. The maximum line length will be one less
+ *                  than size, to accommodate for the null terminator.
+ *                  The minimum buffer size is 1.
+ *
+ * @return  length of the read line, excluding the terminator, if reading was
+ *          successful.
+ * @return  EOF, if the end of the input stream was reached.
+ * @return  -ENOBUFS if the buffer size was exceeded.
+ */
+int readline(char *buf, size_t size);
+
 #ifndef __cplusplus
 /**
  * @brief   Define shell command
diff --git a/sys/shell/shell.c b/sys/shell/shell.c
index 5b89a7fd00..621322aca2 100644
--- a/sys/shell/shell.c
+++ b/sys/shell/shell.c
@@ -439,30 +439,7 @@ static inline void new_line(void)
     }
 }
 
-/**
- * @brief   Read a single line from standard input into a buffer.
- *
- * In addition to copying characters, this routine echoes the line back to
- * stdout and also supports primitive line editing.
- *
- * If the input line is too long, the input will still be consumed until the end
- * to prevent the next line from containing garbage.
- *
- * We allow Unix (\n), DOS (\r\n), and Mac linebreaks (\r).
- * QEMU transmits only a single '\r' == 13 on hitting enter ("-serial stdio").
- * DOS newlines are handled like hitting enter twice.
- *
- * @param   buf     Buffer where the input will be placed.
- * @param   size    Size of the buffer. The maximum line length will be one less
- *                  than size, to accommodate for the null terminator.
- *                  The minimum buffer size is 1.
- *
- * @return  length of the read line, excluding the terminator, if reading was
- *          successful.
- * @return  EOF, if the end of the input stream was reached.
- * @return  -ENOBUFS if the buffer size was exceeded.
- */
-int readline(char *buf, size_t size) /* needed externally by module shell_lock */
+int readline(char *buf, size_t size)
 {
     int curr_pos = 0;
     bool length_exceeded = false;
diff --git a/sys/shell_lock/shell_lock.c b/sys/shell_lock/shell_lock.c
index 8624671066..36bee52f7f 100644
--- a/sys/shell_lock/shell_lock.c
+++ b/sys/shell_lock/shell_lock.c
@@ -52,9 +52,6 @@ static bool _shell_is_locked = true;
 static ztimer_t _shell_auto_lock_ztimer;
 #endif
 
-/* defined in shell.c */
-extern int readline(char *buf, size_t size);
-
 static int _lock_handler(int argc, char **argv)
 {
     (void) argc;