diff --git a/hoplite-aws-kotlin/src/main/kotlin/com/sksamuel/hoplite/aws/kotlin/AwsSecretsManagerPreprocessor.kt b/hoplite-aws-kotlin/src/main/kotlin/com/sksamuel/hoplite/aws/kotlin/AwsSecretsManagerPreprocessor.kt
index 7d93784b..28225e0f 100644
--- a/hoplite-aws-kotlin/src/main/kotlin/com/sksamuel/hoplite/aws/kotlin/AwsSecretsManagerPreprocessor.kt
+++ b/hoplite-aws-kotlin/src/main/kotlin/com/sksamuel/hoplite/aws/kotlin/AwsSecretsManagerPreprocessor.kt
@@ -29,9 +29,15 @@ import kotlinx.serialization.json.Json
  */
 class AwsSecretsManagerPreprocessor(
   private val report: Boolean = false,
+  private val json: Json,
   createClient: () -> SecretsManagerClient = { runBlocking { SecretsManagerClient.fromEnvironment() } }
 ) : TraversingPrimitivePreprocessor() {
 
+  constructor(
+    report: Boolean = false,
+    createClient: () -> SecretsManagerClient = { runBlocking { SecretsManagerClient.fromEnvironment() } }
+  ) : this(report, Json.Default, createClient)
+
   private val client by lazy { createClient() }
   private val regex1 = "\\$\\{awssecret:(.+?)}".toRegex()
   private val regex2 = "secretsmanager://(.+?)".toRegex()
@@ -87,7 +93,7 @@ class AwsSecretsManagerPreprocessor(
             .withMeta(CommonMetadata.RemoteLookup, "AWS '$key'")
             .valid()
         } else {
-          val map = runCatching { Json.Default.decodeFromString<Map<String, String>>(secret) }.getOrElse { emptyMap() }
+          val map = runCatching { json.decodeFromString<Map<String, String>>(secret) }.getOrElse { emptyMap() }
           val indexedValue = map[index]
           if (indexedValue == null)
             ConfigFailure.PreprocessorWarning(