diff --git a/README.md b/README.md
index 86ca9a4f..846d23fb 100644
--- a/README.md
+++ b/README.md
@@ -140,6 +140,13 @@ The majority of scripts is licensed under ASL 2.0 (including codes from Diffuser
 
 ## Change History
 
+### 16 May 2023, 2023/05/16
+
+- Fixed an issue where an error would occur if the encoding of the prompt file was different from the default. [PR #510](https://github.com/kohya-ss/sd-scripts/pull/510) Thanks to sdbds!
+  - Please save the prompt file in UTF-8.
+- プロンプトファイルのエンコーディングがデフォルトと異なる場合にエラーが発生する問題を修正しました。 [PR #510](https://github.com/kohya-ss/sd-scripts/pull/510) sdbds氏に感謝します。
+  - プロンプトファイルはUTF-8で保存してください。
+
 ### 15 May 2023, 2023/05/15
 
 - Added [English translation of documents](https://github.com/darkstorm2150/sd-scripts#links-to-usage-documentation) by darkstorm2150. Thank you very much!
diff --git a/library/train_util.py b/library/train_util.py
index 7c821c82..0bd87bc8 100644
--- a/library/train_util.py
+++ b/library/train_util.py
@@ -3308,15 +3308,15 @@ def sample_images(
     #     prompts = f.readlines()
 
     if args.sample_prompts.endswith(".txt"):
-        with open(args.sample_prompts, "r") as f:
+        with open(args.sample_prompts, "r", encoding="utf-8") as f:
             lines = f.readlines()
         prompts = [line.strip() for line in lines if len(line.strip()) > 0 and line[0] != "#"]
     elif args.sample_prompts.endswith(".toml"):
-        with open(args.sample_prompts, "r") as f:
+        with open(args.sample_prompts, "r", encoding="utf-8") as f:
             data = toml.load(f)
         prompts = [dict(**data["prompt"], **subset) for subset in data["prompt"]["subset"]]
     elif args.sample_prompts.endswith(".json"):
-        with open(args.sample_prompts, "r") as f:
+        with open(args.sample_prompts, "r", encoding="utf-8") as f:
             prompts = json.load(f)
 
     # schedulerを用意する