diff --git a/src/main/scala/firrtl/passes/InferTypes.scala b/src/main/scala/firrtl/passes/InferTypes.scala
index 78213f49e8..4702a87f7c 100644
--- a/src/main/scala/firrtl/passes/InferTypes.scala
+++ b/src/main/scala/firrtl/passes/InferTypes.scala
@@ -12,8 +12,11 @@ object InferTypes extends Pass with PreservesAll[Transform] {
 
   override def prerequisites = Dependency(ResolveKinds) +: firrtl.stage.Forms.WorkingIR
 
+  @deprecated("This should never have been public", "1.3.2")
   type TypeMap = collection.mutable.LinkedHashMap[String, Type]
 
+  private type TypeLookup = collection.mutable.HashMap[String, Type]
+
   def run(c: Circuit): Circuit = {
     val namespace = Namespace()
     val mtypes = (c.modules map (m => m.name -> module_type(m))).toMap
@@ -36,7 +39,7 @@ object InferTypes extends Pass with PreservesAll[Transform] {
       }
     }
 
-    def infer_types_e(types: TypeMap)(e: Expression): Expression =
+    def infer_types_e(types: TypeLookup)(e: Expression): Expression =
       e map infer_types_e(types) match {
         case e: WRef => e copy (tpe = types(e.name))
         case e: WSubField => e copy (tpe = field_type(e.expr.tpe, e.name))
@@ -48,7 +51,7 @@ object InferTypes extends Pass with PreservesAll[Transform] {
         case e @ (_: UIntLiteral | _: SIntLiteral) => e
       }
 
-    def infer_types_s(types: TypeMap)(s: Statement): Statement = s match {
+    def infer_types_s(types: TypeLookup)(s: Statement): Statement = s match {
       case sx: WDefInstance =>
         val t = mtypes(sx.module)
         types(sx.name) = t
@@ -61,7 +64,7 @@ object InferTypes extends Pass with PreservesAll[Transform] {
         val sxx = (sx map infer_types_e(types)).asInstanceOf[DefNode]
         val t = remove_unknowns(sxx.value.tpe)
         types(sx.name) = t
-        sxx map infer_types_e(types)
+        sxx
       case sx: DefRegister =>
         val t = remove_unknowns(sx.tpe)
         types(sx.name) = t
@@ -73,14 +76,14 @@ object InferTypes extends Pass with PreservesAll[Transform] {
       case sx => sx map infer_types_s(types) map infer_types_e(types)
     }
 
-    def infer_types_p(types: TypeMap)(p: Port): Port = {
+    def infer_types_p(types: TypeLookup)(p: Port): Port = {
       val t = remove_unknowns(p.tpe)
       types(p.name) = t
       p copy (tpe = t)
     }
 
     def infer_types(m: DefModule): DefModule = {
-      val types = new TypeMap
+      val types = new TypeLookup
       m map infer_types_p(types) map infer_types_s(types)
     }
 
@@ -92,12 +95,15 @@ object CInferTypes extends Pass with PreservesAll[Transform] {
 
   override def prerequisites = firrtl.stage.Forms.ChirrtlForm
 
+  @deprecated("This should never have been public", "1.3.2")
   type TypeMap = collection.mutable.LinkedHashMap[String, Type]
 
+  private type TypeLookup = collection.mutable.HashMap[String, Type]
+
   def run(c: Circuit): Circuit = {
     val mtypes = (c.modules map (m => m.name -> module_type(m))).toMap
 
-    def infer_types_e(types: TypeMap)(e: Expression) : Expression =
+    def infer_types_e(types: TypeLookup)(e: Expression) : Expression =
       e map infer_types_e(types) match {
          case (e: Reference) => e copy (tpe = types.getOrElse(e.name, UnknownType))
          case (e: SubField) => e copy (tpe = field_type(e.expr.tpe, e.name))
@@ -109,7 +115,7 @@ object CInferTypes extends Pass with PreservesAll[Transform] {
          case e @ (_: UIntLiteral | _: SIntLiteral) => e
       }
 
-    def infer_types_s(types: TypeMap)(s: Statement): Statement = s match {
+    def infer_types_s(types: TypeLookup)(s: Statement): Statement = s match {
       case sx: DefRegister =>
         types(sx.name) = sx.tpe
         sx map infer_types_e(types)
@@ -136,13 +142,13 @@ object CInferTypes extends Pass with PreservesAll[Transform] {
       case sx => sx map infer_types_s(types) map infer_types_e(types)
     }
 
-    def infer_types_p(types: TypeMap)(p: Port): Port = {
+    def infer_types_p(types: TypeLookup)(p: Port): Port = {
       types(p.name) = p.tpe
       p
     }
 
     def infer_types(m: DefModule): DefModule = {
-      val types = new TypeMap
+      val types = new TypeLookup
       m map infer_types_p(types) map infer_types_s(types)
     }