diff --git a/ivy/src/main/scala/sbt/IvyActions.scala b/ivy/src/main/scala/sbt/IvyActions.scala
index 988809fb0..4d69ae2c7 100644
--- a/ivy/src/main/scala/sbt/IvyActions.scala
+++ b/ivy/src/main/scala/sbt/IvyActions.scala
@@ -31,10 +31,10 @@ final case class GetClassifiersConfiguration(module: GetClassifiersModule, exclu
 final case class GetClassifiersModule(id: ModuleID, modules: Seq[ModuleID], configurations: Seq[Configuration], classifiers: Seq[String])
 
 final class UnresolvedWarningConfiguration private[sbt] (
-  val modulePositions: Seq[(ModuleID, SourcePosition)])
+  val modulePositions: Map[ModuleID, SourcePosition])
 object UnresolvedWarningConfiguration {
-  def apply(): UnresolvedWarningConfiguration = apply(Seq())
-  def apply(modulePositions: Seq[(ModuleID, SourcePosition)]): UnresolvedWarningConfiguration =
+  def apply(): UnresolvedWarningConfiguration = apply(Map())
+  def apply(modulePositions: Map[ModuleID, SourcePosition]): UnresolvedWarningConfiguration =
     new UnresolvedWarningConfiguration(modulePositions)
 }