diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4ae22fd..3d81f64 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -60,6 +60,10 @@ elseif(CMAKE_BUILD_TYPE STREQUAL "Testing")
         add_executable(keyboard_activate_deactivate_get_modifier tests/keyboard_activate_deactivate_get_modifier.c)
         target_link_libraries(keyboard_activate_deactivate_get_modifier squirrel)
         add_test(NAME keyboard_activate_deactivate_get_modifier COMMAND keyboard_activate_deactivate_get_modifier)
+
+        add_executable(multikey tests/multikey.c)
+        target_link_libraries(multikey squirrel)
+        add_test(NAME multikey COMMAND multikey)
 else()
        add_compile_options(-Os) # Enable size optimizations
 endif()
diff --git a/tests/multikey.c b/tests/multikey.c
new file mode 100644
index 0000000..356e53e
--- /dev/null
+++ b/tests/multikey.c
@@ -0,0 +1,164 @@
+#include "squirrel.h"
+#include "squirrel_init.h"
+#include "squirrel_key.h"
+#include "squirrel_quantum.h"
+#include <stdarg.h>
+#include <stdlib.h>
+
+uint8_t test_result = 1;
+
+enum squirrel_error test_press(struct key *key, uint8_t layer,
+                               uint8_t key_index, int arg_count, void **args) {
+  (void)layer;
+  (void)key_index;
+
+  if (arg_count != 2) {
+    return ERR_KEY_FUNC_WRONG_ARGUMENT_COUNT;
+  };
+  uint8_t code1 = *(uint8_t *)args[0];
+  uint8_t code2 = *(uint8_t *)args[1];
+  if (code1 == 0x0F && code2 == 0xF0) {
+    test_result = 0;
+  }
+  return ERR_NONE;
+}
+
+enum squirrel_error test_release(struct key *key, uint8_t layer,
+                                 uint8_t key_index, int arg_count,
+                                 void **args) {
+  (void)layer;
+  (void)key_index;
+
+  if (arg_count != 2) {
+    return ERR_KEY_FUNC_WRONG_ARGUMENT_COUNT;
+  };
+  uint8_t code1 = *(uint8_t *)args[0];
+  uint8_t code2 = *(uint8_t *)args[1];
+  if (code1 == 0xF0 && code2 == 0x0F) {
+    test_result = 0;
+  }
+  return ERR_NONE;
+}
+
+// test: press_key, release_key + check_key - in squirrel_key.c,
+// but with multiple keys in a keyboard.
+int main() {
+  squirrel_init(1);
+
+  // press_key + release_key
+  uint8_t code1 = 0x0F;
+  uint8_t code2 = 0xF0;
+
+  struct key testkey;
+  testkey.pressed = test_press;
+  testkey.pressed_argument_count = 2;
+  testkey.pressed_arguments = malloc(2 * sizeof(void *));
+  testkey.pressed_arguments[0] = &code1;
+  testkey.pressed_arguments[1] = &code2;
+
+  testkey.released = test_release;
+  testkey.released_argument_count = 2;
+  testkey.released_arguments = malloc(2 * sizeof(void *));
+  testkey.released_arguments[0] = &code2;
+  testkey.released_arguments[1] = &code1;
+
+  layers[0].keys[0] = testkey;
+  layers[0].keys[1] = testkey;
+  layers[0].keys[2] = testkey;
+  layers[0].keys[3] = testkey;
+  layers[0].keys[4] = testkey;
+  layers[0].active = true;
+
+  for (int i = 0; i < 5; i++) {
+    // check that arguments are correct, and in the correct order.
+    enum squirrel_error err = press_key(i);
+    if (err != ERR_NONE) {
+      return 2;
+    }
+    if (test_result != 0) {
+      return 3;
+    }
+    // keys are copied to layer 17 (index 16) when pressed, to avoid layer
+    // issues.
+    if (layers[16].keys[i].pressed_arguments[0] != &code1) {
+      return 4;
+    }
+    if (layers[16].keys[i].pressed_arguments[1] != &code2) {
+      return 5;
+    }
+
+    test_result = 1;
+    err = release_key(i);
+    if (err != ERR_NONE) {
+      return 6;
+    }
+    if (test_result != 0) {
+      return 7;
+    }
+    // Keys are replaced with passthrough on layer 17 when released.
+    if (layers[16].keys[i].pressed_arguments != NULL) {
+      return 8;
+    }
+    if (layers[16].keys[i].released_arguments != NULL) {
+      return 9;
+    }
+
+    // check_key
+    test_result = 1;
+    key_states[i] = false;
+    err = check_key(i, true); // should call press_key
+    if (err != ERR_NONE) {
+      return 10;
+    }
+    if (test_result != 0) {
+      return 11;
+    }
+    if (key_states[i] != true) {
+      return 12;
+    }
+
+    test_result = 1;
+    key_states[i] = true;
+    err = check_key(i, false); // should call release_key
+    if (err != ERR_NONE) {
+      return 13;
+    }
+    if (test_result != 0) {
+      return 14;
+    }
+    if (key_states[i] != false) {
+      return 15;
+    }
+
+    test_result = 1;
+    key_states[i] = true;
+    err = check_key(i, true); // should not call press_key
+    if (err != ERR_NONE) {
+      return 16;
+    }
+    if (test_result != 1) {
+      return 17;
+    }
+    if (key_states[i] != true) {
+      return 18;
+    }
+
+    test_result = 1;
+    key_states[i] = false;
+    err = check_key(i, false); // should not call release_key
+    if (err != ERR_NONE) {
+      return 19;
+    }
+    if (test_result != 1) {
+      return 20;
+    }
+    if (key_states[i] != false) {
+      return 21;
+    }
+  };
+
+  free(testkey.pressed_arguments);
+  free(testkey.released_arguments);
+
+  return 0;
+}