diff --git a/src/main/scala/diplomacy/LazyModule.scala b/src/main/scala/diplomacy/LazyModule.scala
index 5849657f5d7..75231d4e580 100644
--- a/src/main/scala/diplomacy/LazyModule.scala
+++ b/src/main/scala/diplomacy/LazyModule.scala
@@ -116,9 +116,12 @@ abstract class LazyModule()(implicit val p: Parameters) {
     val nodeDangles = nodes.reverse.flatMap(n => n.cloneDangles())
     val allDangles = nodeDangles ++ childDangles
     val pairing = SortedMap(allDangles.groupBy(_.source).toSeq: _*)
-    val done = Set() ++ pairing.values.filter(_.size == 2).map { case Seq(a, b) =>
-      require(a.flipped != b.flipped)
-      a.source
+    val done = Set() ++ pairing.values.filter(_.size == 2).map { 
+      case Seq(a, b) =>
+        require(a.flipped != b.flipped)
+        a.source
+      case _ =>
+        None
     }
     val forward = allDangles.filter(d => !done(d.source))
     val dangles = forward.map { d =>
@@ -346,15 +349,18 @@ sealed trait LazyModuleImpLike extends RawModule {
     // For each [[source]] set of [[Dangle]]s of size 2, ensure that these
     // can be connected as a source-sink pair (have opposite flipped value).
     // Make the connection and mark them as [[done]].
-    val done = Set() ++ pairing.values.filter(_.size == 2).map { case Seq(a, b) =>
-      require(a.flipped != b.flipped)
-      // @todo <> in chisel3 makes directionless connection.
-      if (a.flipped) {
-        a.data <> b.data
-      } else {
-        b.data <> a.data
-      }
-      a.source
+    val done = Set() ++ pairing.values.filter(_.size == 2).map { 
+      case Seq(a, b) =>
+        require(a.flipped != b.flipped)
+        // @todo <> in chisel3 makes directionless connection.
+        if (a.flipped) {
+          a.data <> b.data
+        } else {
+          b.data <> a.data
+        }
+        a.source
+      case _ =>
+        None
     }
     // Find all [[Dangle]]s which are still not connected. These will end up as [[AutoBundle]] [[IO]] ports on the module.
     val forward = allDangles.filter(d => !done(d.source))