diff --git a/FloconAndroid/flocon-base/src/main/java/io/github/openflocon/flocon/plugins/network/model/BadQualityConfig.kt b/FloconAndroid/flocon-base/src/main/java/io/github/openflocon/flocon/plugins/network/model/BadQualityConfig.kt
index 6965d8fd..2fb94700 100644
--- a/FloconAndroid/flocon-base/src/main/java/io/github/openflocon/flocon/plugins/network/model/BadQualityConfig.kt
+++ b/FloconAndroid/flocon-base/src/main/java/io/github/openflocon/flocon/plugins/network/model/BadQualityConfig.kt
@@ -1,5 +1,6 @@
 package io.github.openflocon.flocon.plugins.network.model
 
+import io.github.openflocon.flocon.FloconLogger
 import kotlin.random.Random
 
 data class BadQualityConfig(
@@ -36,8 +37,13 @@ data class BadQualityConfig(
                 val classPath: String,
             ) : Type {
                 fun generate() : Throwable? {
-                    val errorClass = Class.forName(classPath)
-                    return errorClass.newInstance() as? Throwable
+                    return try {
+                        val errorClass = Class.forName(classPath)
+                        errorClass.newInstance() as? Throwable
+                    } catch (t: Throwable) {
+                        FloconLogger.logError("BadQualityConfig error, className not found", t)
+                        null
+                    }
                 }
             }
         }
diff --git a/FloconAndroid/flocon/src/main/java/io/github/openflocon/flocon/plugins/network/mapper/BadQualityToJson.kt b/FloconAndroid/flocon/src/main/java/io/github/openflocon/flocon/plugins/network/mapper/BadQualityToJson.kt
index 9c38fa00..1d8d2b41 100644
--- a/FloconAndroid/flocon/src/main/java/io/github/openflocon/flocon/plugins/network/mapper/BadQualityToJson.kt
+++ b/FloconAndroid/flocon/src/main/java/io/github/openflocon/flocon/plugins/network/mapper/BadQualityToJson.kt
@@ -68,7 +68,7 @@ fun parseBadQualityConfig(jsonString: String): BadQualityConfig? {
                 val errorContentType = errorObject.optString("errorContentType")
                 val error = BadQualityConfig.Error(
                     weight = errorObject.getDouble("weight").toFloat(),
-                    type = if (errorException.isNotEmpty()) {
+                    type = if (errorException.isNotEmpty() && errorException != "null") {
                         BadQualityConfig.Error.Type.ErrorThrow(errorException)
                     } else {
                         BadQualityConfig.Error.Type.Body(