diff --git a/homeassistant/components/generic_thermostat/config_flow.py b/homeassistant/components/generic_thermostat/config_flow.py
index 5dbccfabe8c..564d7bc01a3 100644
--- a/homeassistant/components/generic_thermostat/config_flow.py
+++ b/homeassistant/components/generic_thermostat/config_flow.py
@@ -116,7 +116,11 @@ async def _validate_config(
 
 
 CONFIG_FLOW = {
-    "user": SchemaFlowFormStep(vol.Schema(CONFIG_SCHEMA), next_step="presets"),
+    "user": SchemaFlowFormStep(
+        vol.Schema(CONFIG_SCHEMA),
+        validate_user_input=_validate_config,
+        next_step="presets",
+    ),
     "presets": SchemaFlowFormStep(vol.Schema(PRESETS_SCHEMA)),
 }
 
diff --git a/homeassistant/components/generic_thermostat/strings.json b/homeassistant/components/generic_thermostat/strings.json
index d81889c83cd..9fe1091d334 100644
--- a/homeassistant/components/generic_thermostat/strings.json
+++ b/homeassistant/components/generic_thermostat/strings.json
@@ -1,5 +1,8 @@
 {
   "config": {
+    "error": {
+      "min_max_runtime": "Minimum run time must be less than the maximum run time."
+    },
     "step": {
       "presets": {
         "data": {
@@ -45,7 +48,7 @@
   },
   "options": {
     "error": {
-      "min_max_runtime": "Minimum run time must be less than the maximum run time."
+      "min_max_runtime": "[%key:component::generic_thermostat::config::error::min_max_runtime%]"
     },
     "step": {
       "init": {