diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/Proto.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/Proto.kt
index 56920ebb3..6df1a8bd1 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/Proto.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/Proto.kt
@@ -112,7 +112,7 @@ class ProtoMap(map: MutableMap<ProtoFieldId, Any>) : MutableMap<ProtoFieldId, An
     }*/
 }
 
-fun Any.contentToString(prefix: String = ""): String = when (this) {
+internal fun Any.contentToString(prefix: String = ""): String = when (this) {
     is UInt -> "0x" + this.toUHexString("") + "($this)"
     is UByte -> "0x" + this.toUHexString() + "($this)"
     is UShort -> "0x" + this.toUHexString("") + "($this)"