diff --git a/esphome/core/__init__.py b/esphome/core/__init__.py
index 6e3f91af22f..5fcad90a81a 100644
--- a/esphome/core/__init__.py
+++ b/esphome/core/__init__.py
@@ -715,6 +715,7 @@ class EsphomeCore:
         self.defines = set()
         self.platformio_options = {}
         self.loaded_integrations = set()
+        self.loaded_platforms = set()
         self.component_ids = set()
         self.platform_counts = defaultdict(int)
         self.unique_ids = {}