diff --git a/README.md b/README.md
index 273b0637..8f8c4487 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,7 @@ It is possible to write timed macros into the center column:
 - `k(1).k(2)` 1, 2
 - `r(3, k(a).w(500))` a, a, a with 500ms pause
 - `m(Control_L, k(a).k(x))` CTRL + a, CTRL + x
+- `h(k(1))` writes ones while the key is pressed down
 
 Documentation:
 - `r` repeats the execution of the second parameter
@@ -31,7 +32,8 @@ Documentation:
 - `h` executes the parameter as long as the key is pressed down
 - `.` executes two actions behind each other
 
-Syntax errors are logged to the console.
+Syntax errors are logged to the console. each `k` function adds a short delay
+of 10ms that can be configured in `~/.config/key-mapper/config`.
 
 ##### Names
 
diff --git a/keymapper/dev/keycode_mapper.py b/keymapper/dev/keycode_mapper.py
index c3f51e09..2a67a0b6 100644
--- a/keymapper/dev/keycode_mapper.py
+++ b/keymapper/dev/keycode_mapper.py
@@ -90,6 +90,15 @@ def handle_keycode(code_to_code, macros, event, uinput):
             # only key-down events trigger macros
             return
 
+        existing_macro = active_macros.get(input_keycode)
+        if existing_macro is not None:
+            # make sure that a duplicate key-down event won't make a
+            # macro with a hold function run forever. there should always
+            # be only one active.
+            # TODO test, throw in a ton of key-down events and one key up
+            #  event and check that no macro is writing stuff
+            existing_macro.release_key()
+
         macro = macros[input_keycode]
         active_macros[input_keycode] = macro
         # TODO test that holding is true