diff --git a/espanso/src/cli/worker/engine/mod.rs b/espanso/src/cli/worker/engine/mod.rs
index cb77ab1..f80d254 100644
--- a/espanso/src/cli/worker/engine/mod.rs
+++ b/espanso/src/cli/worker/engine/mod.rs
@@ -53,8 +53,8 @@ pub fn initialize_and_spawn(
 
       let modulo_manager = ui::modulo::ModuloManager::new();
 
-      let detect_source = super::engine::source::detect::init_and_spawn()
-        .expect("failed to initialize detector module");
+      let (detect_source, modifier_state_store) =
+        super::engine::source::init_and_spawn().expect("failed to initialize detector module");
       let sources: Vec<&dyn crate::engine::funnel::Source> = vec![&detect_source];
       let funnel = crate::engine::funnel::default(&sources);
 
@@ -85,7 +85,8 @@ pub fn initialize_and_spawn(
         &paths.packages,
       );
       let shell_extension = espanso_render::extension::shell::ShellExtension::new(&paths.config);
-      let form_adapter = ui::modulo::form::ModuloFormProviderAdapter::new(&modulo_manager, icon_paths.form_icon);
+      let form_adapter =
+        ui::modulo::form::ModuloFormProviderAdapter::new(&modulo_manager, icon_paths.form_icon);
       let form_extension = espanso_render::extension::form::FormExtension::new(&form_adapter);
       let renderer = espanso_render::create(vec![
         &clipboard_extension,
@@ -106,6 +107,7 @@ pub fn initialize_and_spawn(
         &multiplexer,
         &renderer_adapter,
         &match_cache,
+        &modifier_state_store,
       );
 
       let event_injector =
diff --git a/espanso/src/cli/worker/engine/source/detect.rs b/espanso/src/cli/worker/engine/source/detect.rs
index ce056e9..7d931d5 100644
--- a/espanso/src/cli/worker/engine/source/detect.rs
+++ b/espanso/src/cli/worker/engine/source/detect.rs
@@ -17,22 +17,19 @@
  * along with espanso.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-use anyhow::Result;
 use crossbeam::channel::{Receiver, Select, SelectedOperation};
-use espanso_detect::{event::InputEvent, Source};
-use log::{error, trace};
+use espanso_detect::{event::InputEvent};
 
 use crate::engine::{
   event::{
     input::{Key, KeyboardEvent, MouseButton, MouseEvent, Status, Variant},
     Event,
   },
-  funnel, process,
+  funnel
 };
-use thiserror::Error;
 
 pub struct DetectSource {
-  receiver: Receiver<InputEvent>,
+  pub receiver: Receiver<InputEvent>,
 }
 
 impl<'a> funnel::Source<'a> for DetectSource {
@@ -60,67 +57,6 @@ impl<'a> funnel::Source<'a> for DetectSource {
   }
 }
 
-// TODO: pass options
-pub fn init_and_spawn() -> Result<DetectSource> {
-  let (sender, receiver) = crossbeam::channel::unbounded();
-  let (init_tx, init_rx) = crossbeam::channel::unbounded();
-
-  if let Err(error) = std::thread::Builder::new()
-    .name("detect thread".to_string())
-    .spawn(
-      move || match espanso_detect::get_source(Default::default()) {
-        Ok(mut source) => {
-          if source.initialize().is_err() {
-            init_tx
-              .send(false)
-              .expect("unable to send to the init_tx channel");
-          } else {
-            init_tx
-              .send(true)
-              .expect("unable to send to the init_tx channel");
-
-            source
-              .eventloop(Box::new(move |event| {
-                sender
-                  .send(event)
-                  .expect("unable to send to the source channel");
-              }))
-              .expect("detect eventloop crashed");
-          }
-        }
-        Err(error) => {
-          error!("cannot initialize event source: {:?}", error);
-          init_tx
-            .send(false)
-            .expect("unable to send to the init_tx channel");
-        }
-      },
-    )
-  {
-    error!("detection thread initialization failed: {:?}", error);
-    return Err(DetectSourceError::ThreadInitFailed.into());
-  }
-
-  // Wait for the initialization status
-  let has_initialized = init_rx
-    .recv()
-    .expect("unable to receive from the init_rx channel");
-  if !has_initialized {
-    return Err(DetectSourceError::InitFailed.into());
-  }
-
-  Ok(DetectSource { receiver })
-}
-
-#[derive(Error, Debug)]
-pub enum DetectSourceError {
-  #[error("detection thread initialization failed")]
-  ThreadInitFailed,
-
-  #[error("detection source initialization failed")]
-  InitFailed,
-}
-
 impl From<espanso_detect::event::Key> for Key {
   fn from(key: espanso_detect::event::Key) -> Self {
     match key {
diff --git a/espanso/src/cli/worker/engine/source/mod.rs b/espanso/src/cli/worker/engine/source/mod.rs
index e5f4092..788e985 100644
--- a/espanso/src/cli/worker/engine/source/mod.rs
+++ b/espanso/src/cli/worker/engine/source/mod.rs
@@ -17,4 +17,105 @@
  * along with espanso.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-pub mod detect;
\ No newline at end of file
+use anyhow::Result;
+use espanso_detect::event::{InputEvent, KeyboardEvent, Status};
+use log::{error};
+use thiserror::Error;
+
+use detect::DetectSource;
+
+use self::modifier::{Modifier, ModifierStateStore};
+
+pub mod detect;
+pub mod modifier;
+
+// TODO: pass options
+pub fn init_and_spawn() -> Result<(DetectSource, ModifierStateStore)> {
+  let (sender, receiver) = crossbeam::channel::unbounded();
+  let (init_tx, init_rx) = crossbeam::channel::unbounded();
+
+  let modifier_state_store = ModifierStateStore::new();
+
+  let state_store_clone = modifier_state_store.clone();
+  if let Err(error) = std::thread::Builder::new()
+    .name("detect thread".to_string())
+    .spawn(
+      move || match espanso_detect::get_source(Default::default()) {
+        Ok(mut source) => {
+          if source.initialize().is_err() {
+            init_tx
+              .send(false)
+              .expect("unable to send to the init_tx channel");
+          } else {
+            init_tx
+              .send(true)
+              .expect("unable to send to the init_tx channel");
+
+            source
+              .eventloop(Box::new(move |event| {
+                // Update the modifiers state
+                if let Some((modifier, is_pressed)) = get_modifier_status(&event) {
+                  state_store_clone.update_state(modifier, is_pressed);
+                }
+
+                sender
+                  .send(event)
+                  .expect("unable to send to the source channel");
+              }))
+              .expect("detect eventloop crashed");
+          }
+        }
+        Err(error) => {
+          error!("cannot initialize event source: {:?}", error);
+          init_tx
+            .send(false)
+            .expect("unable to send to the init_tx channel");
+        }
+      },
+    )
+  {
+    error!("detection thread initialization failed: {:?}", error);
+    return Err(DetectSourceError::ThreadInitFailed.into());
+  }
+
+  // Wait for the initialization status
+  let has_initialized = init_rx
+    .recv()
+    .expect("unable to receive from the init_rx channel");
+  if !has_initialized {
+    return Err(DetectSourceError::InitFailed.into());
+  }
+
+  Ok((DetectSource { receiver }, modifier_state_store))
+}
+
+#[derive(Error, Debug)]
+pub enum DetectSourceError {
+  #[error("detection thread initialization failed")]
+  ThreadInitFailed,
+
+  #[error("detection source initialization failed")]
+  InitFailed,
+}
+
+fn get_modifier_status(event: &InputEvent) -> Option<(Modifier, bool)> {
+  match event {
+    InputEvent::Keyboard(KeyboardEvent {
+      key,
+      status,
+      value: _,
+      variant: _,
+      code: _,
+    }) => {
+      let is_pressed = *status == Status::Pressed;
+      match key {
+        espanso_detect::event::Key::Alt => Some((Modifier::Alt, is_pressed)),
+        espanso_detect::event::Key::Control => Some((Modifier::Ctrl, is_pressed)), 
+        espanso_detect::event::Key::Meta => Some((Modifier::Meta, is_pressed)), 
+        espanso_detect::event::Key::Shift => Some((Modifier::Shift, is_pressed)),
+        _ => None 
+      }
+    }
+    _ => None,
+  }
+}
diff --git a/espanso/src/cli/worker/engine/source/modifier.rs b/espanso/src/cli/worker/engine/source/modifier.rs
new file mode 100644
index 0000000..02e40b4
--- /dev/null
+++ b/espanso/src/cli/worker/engine/source/modifier.rs
@@ -0,0 +1,134 @@
+/*
+ * This file is part of espanso.
+ *
+ * Copyright (C) 2019-2021 Federico Terzi
+ *
+ * espanso is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * espanso is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with espanso.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+use std::{
+  sync::{Arc, Mutex},
+  time::{Duration, Instant},
+};
+
+use log::warn;
+
+use crate::engine::process::ModifierStatusProvider;
+
+// TODO: explain
+const MAXIMUM_MODIFIERS_PRESS_TIME_RECORD: Duration = Duration::from_secs(30);
+
+#[derive(Debug, Hash, PartialEq, Eq)]
+pub enum Modifier {
+  Ctrl,
+  Shift,
+  Alt,
+  Meta,
+}
+
+#[derive(Clone)]
+pub struct ModifierStateStore {
+  state: Arc<Mutex<ModifiersState>>,
+}
+
+impl ModifierStateStore {
+  pub fn new() -> Self {
+    Self {
+      state: Arc::new(Mutex::new(ModifiersState::default())),
+    }
+  }
+
+  pub fn is_any_modifier_pressed(&self) -> bool {
+    let mut state = self.state.lock().expect("unable to obtain modifier state");
+    let mut is_any_modifier_pressed = false;
+    for (modifier, status) in &mut state.modifiers {
+      if status.is_outdated() {
+        warn!(
+          "detected outdated modifier records for {:?}, releasing the state",
+          modifier
+        );
+        status.release();
+      }
+
+      if status.is_pressed() {
+        is_any_modifier_pressed = true;
+      }
+    }
+    is_any_modifier_pressed
+  }
+
+  pub fn update_state(&self, modifier: Modifier, is_pressed: bool) {
+    let mut state = self.state.lock().expect("unable to obtain modifier state");
+    for (curr_modifier, status) in &mut state.modifiers {
+      if curr_modifier == &modifier {
+        if is_pressed {
+          status.press();
+        } else {
+          status.release();
+        }
+        break;
+      }
+    }
+  }
+}
+
+struct ModifiersState {
+  modifiers: Vec<(Modifier, ModifierStatus)>,
+}
+
+impl Default for ModifiersState {
+  fn default() -> Self {
+    Self {
+      modifiers: vec![
+        (Modifier::Ctrl, ModifierStatus { pressed_at: None }),
+        (Modifier::Alt, ModifierStatus { pressed_at: None }),
+        (Modifier::Shift, ModifierStatus { pressed_at: None }),
+        (Modifier::Meta, ModifierStatus { pressed_at: None }),
+      ],
+    }
+  }
+}
+
+struct ModifierStatus {
+  pressed_at: Option<Instant>,
+}
+
+impl ModifierStatus {
+  fn is_pressed(&self) -> bool {
+    self.pressed_at.is_some()
+  }
+
+  fn is_outdated(&self) -> bool {
+    let now = Instant::now();
+    if let Some(pressed_at) = self.pressed_at {
+      now.duration_since(pressed_at) > MAXIMUM_MODIFIERS_PRESS_TIME_RECORD
+    } else {
+      false
+    }
+  }
+
+  fn release(&mut self) {
+    self.pressed_at = None
+  }
+
+  fn press(&mut self) {
+    self.pressed_at = Some(Instant::now());
+  }
+}
+
+impl ModifierStatusProvider for ModifierStateStore {
+  fn is_any_modifier_pressed(&self) -> bool {
+    self.is_any_modifier_pressed()
+  }
+}
diff --git a/espanso/src/engine/process/default.rs b/espanso/src/engine/process/default.rs
index 52bf18a..2bfbf3e 100644
--- a/espanso/src/engine/process/default.rs
+++ b/espanso/src/engine/process/default.rs
@@ -22,6 +22,7 @@ use log::trace;
 use super::{Event, MatchFilter, MatchInfoProvider, MatchSelector, Matcher, Middleware, Multiplexer, Processor, Renderer, middleware::{
     match_select::MatchSelectMiddleware, matcher::MatcherMiddleware, multiplex::MultiplexMiddleware,
     render::RenderMiddleware, action::ActionMiddleware, cursor_hint::CursorHintMiddleware, cause::CauseCompensateMiddleware,
+    delay_modifiers::{DelayForModifierReleaseMiddleware, ModifierStatusProvider},
   }};
 use std::collections::VecDeque;
 
@@ -38,6 +39,7 @@ impl<'a> DefaultProcessor<'a> {
     multiplexer: &'a dyn Multiplexer,
     renderer: &'a dyn Renderer<'a>,
     match_info_provider: &'a dyn MatchInfoProvider,
+    modifier_status_provider: &'a dyn ModifierStatusProvider,
   ) -> DefaultProcessor<'a> {
     Self {
       event_queue: VecDeque::new(),
@@ -49,6 +51,7 @@ impl<'a> DefaultProcessor<'a> {
         Box::new(RenderMiddleware::new(renderer)),
         Box::new(CursorHintMiddleware::new()),
         Box::new(ActionMiddleware::new(match_info_provider)),
+        Box::new(DelayForModifierReleaseMiddleware::new(modifier_status_provider)),
       ],
     }
   }
@@ -63,6 +66,7 @@ impl<'a> DefaultProcessor<'a> {
         current_queue.push_front(event);
       };
 
+      trace!("--------------- new event -----------------");
       for middleware in self.middleware.iter() {
         trace!("middleware '{}' received event: {:?}", middleware.name(), current_event);
 
diff --git a/espanso/src/engine/process/middleware/delay_modifiers.rs b/espanso/src/engine/process/middleware/delay_modifiers.rs
new file mode 100644
index 0000000..f6977a4
--- /dev/null
+++ b/espanso/src/engine/process/middleware/delay_modifiers.rs
@@ -0,0 +1,84 @@
+/*
+ * This file is part of espanso.
+ *
+ * Copyright (C) 2019-2021 Federico Terzi
+ *
+ * espanso is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * espanso is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with espanso.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+// TODO: explain why this is needed
+
+use std::{
+  time::{Duration, Instant},
+};
+
+use log::{trace, warn};
+
+use super::super::Middleware;
+use crate::engine::event::{
+  Event,
+};
+
+// TODO: pass through config
+const MODIFIER_DELAY_TIMEOUT: Duration = Duration::from_secs(3);
+
+pub trait ModifierStatusProvider {
+  fn is_any_modifier_pressed(&self) -> bool;
+}
+
+pub struct DelayForModifierReleaseMiddleware<'a> {
+  provider: &'a dyn ModifierStatusProvider,
+}
+
+impl <'a> DelayForModifierReleaseMiddleware<'a> {
+  pub fn new(provider: &'a dyn ModifierStatusProvider) -> Self {
+    Self {
+      provider
+    }
+  }
+}
+
+impl <'a> Middleware for DelayForModifierReleaseMiddleware<'a> {
+  fn name(&self) -> &'static str {
+    "delay_modifiers"
+  }
+
+  fn next(&self, event: Event, _: &mut dyn FnMut(Event)) -> Event {
+    if is_injection_event(&event) {
+      let start = Instant::now();
+      while self.provider.is_any_modifier_pressed() {
+        if Instant::now().duration_since(start) > MODIFIER_DELAY_TIMEOUT {
+          warn!("injection delay has timed out, please release the modifier keys (SHIFT, CTRL, ALT, CMD) to trigger an expansion");
+          break;
+        }
+        trace!("delaying injection event as some modifiers are pressed");
+        std::thread::sleep(Duration::from_millis(100));
+      }
+    }
+
+    event
+  }
+}
+
+fn is_injection_event(event: &Event) -> bool {
+  match event {
+    Event::TriggerCompensation(_) => true,
+    Event::CursorHintCompensation(_) => true,
+    Event::KeySequenceInject(_) => true,
+    Event::TextInject(_) => true,
+    _ => false,
+  }
+}
+
+// TODO: test
diff --git a/espanso/src/engine/process/middleware/mod.rs b/espanso/src/engine/process/middleware/mod.rs
index 91d530f..ff26462 100644
--- a/espanso/src/engine/process/middleware/mod.rs
+++ b/espanso/src/engine/process/middleware/mod.rs
@@ -20,6 +20,7 @@
 pub mod action;
 pub mod cause;
 pub mod cursor_hint;
+pub mod delay_modifiers;
 pub mod match_select;
 pub mod matcher;
 pub mod multiplex;
diff --git a/espanso/src/engine/process/mod.rs b/espanso/src/engine/process/mod.rs
index 51b4370..e88c123 100644
--- a/espanso/src/engine/process/mod.rs
+++ b/espanso/src/engine/process/mod.rs
@@ -93,6 +93,7 @@ pub enum RendererError {
 }
 
 pub use middleware::action::MatchInfoProvider;
+pub use middleware::delay_modifiers::ModifierStatusProvider;
 
 pub fn default<'a, MatcherState>(
   matchers: &'a [&'a dyn Matcher<'a, MatcherState>],
@@ -101,6 +102,7 @@ pub fn default<'a, MatcherState>(
   multiplexer: &'a dyn Multiplexer,
   renderer: &'a dyn Renderer<'a>,
   match_info_provider: &'a dyn MatchInfoProvider,
+  modifier_status_provider: &'a dyn ModifierStatusProvider,
 ) -> impl Processor + 'a {
   default::DefaultProcessor::new(
     matchers,
@@ -109,5 +111,6 @@ pub fn default<'a, MatcherState>(
     multiplexer,
     renderer,
     match_info_provider,
+    modifier_status_provider,
   )
 }