diff --git a/build.sbt b/build.sbt
index 17c3bead8..52f284f75 100644
--- a/build.sbt
+++ b/build.sbt
@@ -192,7 +192,9 @@ val completeProj = (project in file("internal") / "util-complete")
     name := "Completion",
     libraryDependencies += jline,
     mimaSettings,
-    mimaBinaryIssueFilters ++= Seq(
+    // Parser is used publicly, so we can't break bincompat.
+    mimaBinaryIssueFilters := Seq(
+      exclude[DirectMissingMethodProblem]("sbt.internal.util.complete.History.this"),
     ),
   )
   .configure(addSbtIO, addSbtUtilControl)
diff --git a/internal/util-complete/src/main/scala/sbt/internal/util/complete/EditDistance.scala b/internal/util-complete/src/main/scala/sbt/internal/util/complete/EditDistance.scala
index cad2e5002..f0355329e 100644
--- a/internal/util-complete/src/main/scala/sbt/internal/util/complete/EditDistance.scala
+++ b/internal/util-complete/src/main/scala/sbt/internal/util/complete/EditDistance.scala
@@ -24,10 +24,12 @@ object EditDistance {
       insertCost: Int = 1,
       deleteCost: Int = 1,
       subCost: Int = 1,
+      transposeCost: Int = 1,
       matchCost: Int = 0,
       caseCost: Int = 1,
       transpositions: Boolean = false
   ): Int = {
+    val _ = transposeCost
     val n = s.length
     val m = t.length
     if (n == 0) return m
diff --git a/internal/util-complete/src/main/scala/sbt/internal/util/complete/History.scala b/internal/util-complete/src/main/scala/sbt/internal/util/complete/History.scala
index 8c63bf592..52bb7acd5 100644
--- a/internal/util-complete/src/main/scala/sbt/internal/util/complete/History.scala
+++ b/internal/util-complete/src/main/scala/sbt/internal/util/complete/History.scala
@@ -48,6 +48,8 @@ final class History private (val lines: IndexedSeq[String], val path: Option[Fil
 }
 
 object History {
+  def apply(lines: Seq[String], path: Option[File], error: String => Unit): History =
+    new History(lines.toIndexedSeq, path)
   def apply(lines: Seq[String], path: Option[File]): History =
     new History(lines.toIndexedSeq, path)
 
diff --git a/internal/util-complete/src/main/scala/sbt/internal/util/complete/Parser.scala b/internal/util-complete/src/main/scala/sbt/internal/util/complete/Parser.scala
index 31c1ca67a..f72645573 100644
--- a/internal/util-complete/src/main/scala/sbt/internal/util/complete/Parser.scala
+++ b/internal/util-complete/src/main/scala/sbt/internal/util/complete/Parser.scala
@@ -387,7 +387,13 @@ trait ParserMain {
   }
 
   /** Presents a Char range as a Parser.  A single Char is parsed only if it is in the given range.*/
-  implicit def range(r: collection.immutable.NumericRange[Char], label: String): Parser[Char] =
+  implicit def range(r: collection.immutable.NumericRange[Char]): Parser[Char] = {
+    val label = r.map(_.toString).toString
+    range(r, label)
+  }
+
+  /** Presents a Char range as a Parser.  A single Char is parsed only if it is in the given range.*/
+  def range(r: collection.immutable.NumericRange[Char], label: String): Parser[Char] =
     charClass(r contains _, label).examples(r.map(_.toString): _*)
 
   /** Defines a Parser that parses a single character only if it is contained in `legal`.*/
@@ -400,7 +406,7 @@ trait ParserMain {
    * Defines a Parser that parses a single character only if the predicate `f` returns true for that character.
    * If this parser fails, `label` is used as the failure message.
    */
-  def charClass(f: Char => Boolean, label: String): Parser[Char] =
+  def charClass(f: Char => Boolean, label: String = "<unspecified>"): Parser[Char] =
     new CharacterClass(f, label)
 
   /** Presents a single Char `ch` as a Parser that only parses that exact character. */