diff --git a/aioesphomeapi/client.py b/aioesphomeapi/client.py
index 9c48e38..e4859f7 100644
--- a/aioesphomeapi/client.py
+++ b/aioesphomeapi/client.py
@@ -819,10 +819,10 @@ class APIClient:
             req.color_temperature = color_temperature
         if transition_length is not None:
             req.has_transition_length = True
-            req.transition_length = int(round(transition_length / 1000))
+            req.transition_length = int(round(transition_length * 1000))
         if flash_length is not None:
             req.has_flash_length = True
-            req.flash_length = int(round(flash_length / 1000))
+            req.flash_length = int(round(flash_length * 1000))
         if effect is not None:
             req.has_effect = True
             req.effect = effect