diff --git a/app.py b/app.py
index 77958d9..f7e7fa3 100755
--- a/app.py
+++ b/app.py
@@ -13,17 +13,32 @@ from uuid import uuid4
 
 import attr
 import json5
-from quart import (Quart, Response, jsonify, request, safe_join, send_file,
-                   send_from_directory, websocket)
+from quart import (
+    Quart,
+    Response,
+    jsonify,
+    request,
+    safe_join,
+    send_file,
+    send_from_directory,
+    websocket,
+)
 from quart_cors import cors
 from swagger_ui import quart_api_doc
 
 from rhasspy.actor import ActorSystem, ConfigureEvent, RhasspyActor
 from rhasspy.core import RhasspyCore
 from rhasspy.events import IntentRecognized, ProfileTrainingFailed
-from rhasspy.utils import (FunctionLoggingHandler, buffer_to_wav,
-                           get_all_intents, get_ini_paths, get_wav_duration,
-                           load_phoneme_examples, read_dict, recursive_remove)
+from rhasspy.utils import (
+    FunctionLoggingHandler,
+    buffer_to_wav,
+    get_all_intents,
+    get_ini_paths,
+    get_wav_duration,
+    load_phoneme_examples,
+    read_dict,
+    recursive_remove,
+)
 
 # -----------------------------------------------------------------------------
 # Quart Web App Setup
@@ -808,6 +823,16 @@ async def api_slots() -> Union[str, Response]:
         overwrite_all = request.args.get("overwrite_all", "false").lower() == "true"
         new_slot_values = json5.loads(await request.data)
 
+        word_casing = core.profile.get(
+            "speech_to_text.dictionary_casing", "ignore"
+        ).lower()
+        word_transform = lambda s: s
+
+        if word_casing == "lower":
+            word_transform = str.lower
+        elif word_casing == "upper":
+            word_transform = str.upper
+
         slots_dir = Path(
             core.profile.write_path(
                 core.profile.get("speech_to_text.slots_dir", "slots")
@@ -834,15 +859,17 @@ async def api_slots() -> Union[str, Response]:
             slots_path.parent.mkdir(parents=True, exist_ok=True)
 
             # Merge with existing values
-            values = set(values)
+            values = set([word_transform(v.strip()) for v in values])
             if slots_path.is_file():
-                values.update(line for line in slots_path.read_text().splitlines())
+                values.update(
+                    word_transform(line.strip())
+                    for line in slots_path.read_text().splitlines()
+                )
 
             # Write merged values
             if values:
                 with open(slots_path, "w") as slots_file:
                     for value in values:
-                        value = value.strip()
                         if value:
                             print(value, file=slots_file)