diff --git a/src/main/scala/com.snowplowanalytics.iglu/client/ClientError.scala b/src/main/scala/com.snowplowanalytics.iglu/client/ClientError.scala
index a9466151..60f32aa4 100644
--- a/src/main/scala/com.snowplowanalytics.iglu/client/ClientError.scala
+++ b/src/main/scala/com.snowplowanalytics.iglu/client/ClientError.scala
@@ -17,14 +17,14 @@ import java.time.Instant
 import cats.Show
 import cats.syntax.show._
 import cats.syntax.either._
-
 import io.circe.{Decoder, DecodingFailure, Encoder, Json}
 import io.circe.syntax._
-
 import validator.ValidatorError
 import resolver.LookupHistory
 import resolver.registries.RegistryError
 
+import scala.collection.immutable.SortedMap
+
 /** Common type for Resolver's and Validator's errors */
 sealed trait ClientError extends Product with Serializable {
   def getMessage: String =
@@ -34,7 +34,7 @@ sealed trait ClientError extends Product with Serializable {
 object ClientError {
 
   /** Error happened during schema resolution step */
-  final case class ResolutionError(value: Map[String, LookupHistory]) extends ClientError {
+  final case class ResolutionError(value: SortedMap[String, LookupHistory]) extends ClientError {
     def isNotFound: Boolean =
       value.values.flatMap(_.errors).forall(_ == RegistryError.NotFound)
   }
@@ -67,7 +67,7 @@ object ClientError {
               .downField("lookupHistory")
               .as[List[RepoLookupHistory]]
               .map { history =>
-                ResolutionError(history.map(_.toField).toMap)
+                ResolutionError(SortedMap[String, LookupHistory]() ++ history.map(_.toField).toMap)
               }
           case "ValidationError" =>
             cursor
diff --git a/src/main/scala/com.snowplowanalytics.iglu/client/resolver/Resolver.scala b/src/main/scala/com.snowplowanalytics.iglu/client/resolver/Resolver.scala
index f7cd69b1..946e898e 100644
--- a/src/main/scala/com.snowplowanalytics.iglu/client/resolver/Resolver.scala
+++ b/src/main/scala/com.snowplowanalytics.iglu/client/resolver/Resolver.scala
@@ -17,13 +17,10 @@ import cats.{Applicative, Id, Monad}
 import java.time.Instant
 
 import scala.concurrent.duration.MILLISECONDS
-
 import cats.data._
 import cats.effect.Clock
 import cats.implicits._
-
 import io.circe.{Decoder, DecodingFailure, HCursor, Json}
-
 import com.snowplowanalytics.iglu.core.{
   SchemaCriterion,
   SchemaKey,
@@ -34,7 +31,6 @@ import com.snowplowanalytics.iglu.core.{
   SelfDescribingSchema
 }
 import com.snowplowanalytics.iglu.core.circe.CirceIgluCodecs._
-
 import com.snowplowanalytics.iglu.client.ClientError.ResolutionError
 import com.snowplowanalytics.iglu.client.resolver.registries.{
   Registry,
@@ -43,6 +39,8 @@ import com.snowplowanalytics.iglu.client.resolver.registries.{
 }
 import com.snowplowanalytics.iglu.client.resolver.registries.Registry.Get
 
+import scala.collection.immutable.SortedMap
+
 /** Resolves schemas from one or more Iglu schema registries */
 final case class Resolver[F[_]](repos: List[Registry], cache: Option[ResolverCache[F]]) {
   import Resolver._
@@ -295,7 +293,9 @@ object Resolver {
 
   private def postProcess[F[_], A](result: Either[LookupFailureMap, A]) =
     result.leftMap { failure =>
-      ResolutionError(failure.map { case (key, value) => (key.config.name, value) })
+      ResolutionError(SortedMap[String, LookupHistory]() ++ failure.map {
+        case (key, value) => (key.config.name, value)
+      })
     }
 
   private def matchConfig[F[_]: Applicative](datum: SelfDescribingData[Json]) = {
diff --git a/src/test/scala/com.snowplowanalytics.iglu.client/ClientErrorSpec.scala b/src/test/scala/com.snowplowanalytics.iglu.client/ClientErrorSpec.scala
index 5d2c626d..0fac976a 100644
--- a/src/test/scala/com.snowplowanalytics.iglu.client/ClientErrorSpec.scala
+++ b/src/test/scala/com.snowplowanalytics.iglu.client/ClientErrorSpec.scala
@@ -13,16 +13,15 @@
 package com.snowplowanalytics.iglu.client
 
 import cats.data.NonEmptyList
-
 import io.circe.syntax._
 import io.circe.literal._
-
 import com.snowplowanalytics.iglu.client.resolver.LookupHistory
 import com.snowplowanalytics.iglu.client.resolver.registries.RegistryError
 import com.snowplowanalytics.iglu.client.validator.{ValidatorError, ValidatorReport}
-
 import org.specs2.Specification
 
+import scala.collection.immutable.SortedMap
+
 class ClientErrorSpec extends Specification {
   def is =
     s2"""
@@ -32,7 +31,7 @@ class ClientErrorSpec extends Specification {
 
   def e1 = {
     val error: ClientError = ClientError.ResolutionError(
-      Map(
+      SortedMap(
         "First repo" -> LookupHistory(
           Set(RegistryError.NotFound, RegistryError.RepoFailure("Server outage")),
           1,
diff --git a/src/test/scala/com.snowplowanalytics.iglu.client/resolver/ResolverSpec.scala b/src/test/scala/com.snowplowanalytics.iglu.client/resolver/ResolverSpec.scala
index 00f593ad..48f9cc3c 100644
--- a/src/test/scala/com.snowplowanalytics.iglu.client/resolver/ResolverSpec.scala
+++ b/src/test/scala/com.snowplowanalytics.iglu.client/resolver/ResolverSpec.scala
@@ -15,6 +15,8 @@ package com.snowplowanalytics.iglu.client.resolver
 import java.time.Instant
 import java.net.URI
 
+import scala.collection.immutable.SortedMap
+
 // Cats
 import cats.Id
 import cats.effect.IO
@@ -132,7 +134,7 @@ class ResolverSpec extends Specification with DataTables with ValidatedMatchers
 
     val schemaKey = SchemaKey("com.acme.icarus", "wing", "jsonschema", SchemaVer.Full(1, 0, 0))
     val expected = ResolutionError(
-      Map(
+      SortedMap(
         "Iglu Client Embedded" -> LookupHistory(Set(RegistryError.NotFound), 1, SpecHelpers.now),
         "Iglu Test Embedded"   -> LookupHistory(Set(RegistryError.NotFound), 1, SpecHelpers.now)
       ))
@@ -151,7 +153,7 @@ class ResolverSpec extends Specification with DataTables with ValidatedMatchers
         "jsonschema",
         SchemaVer.Full(1, 0, 0))
     val expected = ResolutionError(
-      Map(
+      SortedMap(
         "Iglu Client Embedded" -> LookupHistory(Set(RegistryError.NotFound), 1, SpecHelpers.now),
         "Iglu Test Embedded" -> LookupHistory(
           Set(RegistryError.RepoFailure("ParsingFailure: exhausted input")),
@@ -312,7 +314,7 @@ class ResolverSpec extends Specification with DataTables with ValidatedMatchers
       Nil)
 
     val expected = ResolutionError(
-      Map(
+      SortedMap(
         "Mock Repo 1" -> LookupHistory(Set(error1, error2), 2, Instant.ofEpochMilli(2008L)),
         "Mock Repo 2" -> LookupHistory(Set(error3, error4), 2, Instant.ofEpochMilli(2009L)),
         "Iglu Client Embedded" -> LookupHistory(