diff --git a/packages/backend/src/misc/check-word-mute.ts b/packages/backend/src/misc/check-word-mute.ts
index 8c7d950861..a75beed9d1 100644
--- a/packages/backend/src/misc/check-word-mute.ts
+++ b/packages/backend/src/misc/check-word-mute.ts
@@ -33,7 +33,9 @@ function checkWordMute(
 
 			if (
 				keywords.length > 0 &&
-				keywords.every((keyword) => text.includes(keyword))
+				keywords.every((keyword) =>
+					text.toLowerCase().includes(keyword.toLowerCase()),
+				)
 			)
 				return true;
 		} else {
diff --git a/packages/client/src/scripts/check-word-mute.ts b/packages/client/src/scripts/check-word-mute.ts
index 50188a83ba..bec824fb21 100644
--- a/packages/client/src/scripts/check-word-mute.ts
+++ b/packages/client/src/scripts/check-word-mute.ts
@@ -26,7 +26,9 @@ function checkWordMute(
 
 			if (
 				keywords.length > 0 &&
-				keywords.every((keyword) => text.includes(keyword))
+				keywords.every((keyword) =>
+					text.toLowerCase().includes(keyword.toLowerCase()),
+				)
 			) {
 				result.muted = true;
 				result.matched.push(...keywords);