diff --git a/build.sbt b/build.sbt
index 02c434e..d7773ab 100644
--- a/build.sbt
+++ b/build.sbt
@@ -1,12 +1,13 @@
 import sbtcrossproject.{ crossProject, CrossType }
 
-lazy val catsVersion       = "2.6.1"
-lazy val fs2CoreVersion    = "2.5.6"
+lazy val catsVersion       = "2.7.0"
+lazy val fs2CoreVersion    = "2.5.10"
 lazy val scalacheckVersion = "1.15.4"
 
-lazy val scala212 = "2.12.16"
-lazy val scala213 = "2.13.6"
-lazy val scala30  = "3.0.2"
+lazy val scala212 = "2.12.20"
+lazy val scala213 = "2.13.16"
+lazy val scala30  = "3.3.6"
+lazy val scala31  = "3.7.0"
 
 lazy val commonSettings = Seq(
   organization := "org.tpolecat",
@@ -19,7 +20,8 @@ lazy val commonSettings = Seq(
     ("BSD New", url("http://opensource.org/licenses/BSD-3-Clause"))
   ),
   scalaVersion        := scala213,
-  crossScalaVersions  := Seq(scala212, scala213, scala30),
+  crossScalaVersions  := Seq(scala212, scala213, scala30, scala31),
+  scalacOptions += "-Wconf:msg=infix|vararg|deprecated:s",
 
   // dottydoc really doesn't work at all right now
   Compile / doc / sources := {
@@ -70,7 +72,7 @@ lazy val refined =
     .settings(commonSettings)
     .settings(
       name := "atto-refined",
-      libraryDependencies += "eu.timepit" %%% "refined" % "0.9.26",
+      libraryDependencies += "eu.timepit" %%% "refined" % "0.11.3",
     )
 
 lazy val tests =
diff --git a/modules/core/src/main/scala/atto/parser/Character.scala b/modules/core/src/main/scala/atto/parser/Character.scala
index 8ab0730..869d99c 100644
--- a/modules/core/src/main/scala/atto/parser/Character.scala
+++ b/modules/core/src/main/scala/atto/parser/Character.scala
@@ -5,7 +5,7 @@ import cats.implicits._
 import java.lang.String
 import atto.syntax.parser._
 import scala.{ Char, Boolean, Option, Unit }
-import scala.Predef.{ charWrapper, augmentString }
+import scala.Predef.{ charWrapper, intWrapper, augmentString }
 
 /** Parsers for various kinds of characters. */
 trait Character {
@@ -102,5 +102,5 @@ trait Character {
 
   /** Whitespace that is not a line break */
   def horizontalWhitespace: Parser[Char] =
-    oneOf(" \t") named "horizontalWhitespace"
+    oneOf(s" \t\u00A0\u1680\u180e${(0x2000 to 0x200a).map(_.toChar).mkString}\u202f\u205f\u3000").named("horizontalWhitespace")
 }
diff --git a/modules/core/src/main/scala/atto/parser/Combinator.scala b/modules/core/src/main/scala/atto/parser/Combinator.scala
index f6618a3..1082a11 100644
--- a/modules/core/src/main/scala/atto/parser/Combinator.scala
+++ b/modules/core/src/main/scala/atto/parser/Combinator.scala
@@ -56,7 +56,7 @@ trait Combinator0 {
 
   private def prompt[R](st0: State, kf: State => TResult[R], ks: State => TResult[R]): Result[R] =
     Partial[R](s =>
-      if (s.isEmpty) Eval.defer(kf(st0 copy (complete = true)))
+      if (s.isEmpty) Eval.defer(kf(st0.copy(complete = true)))
       else Eval.defer(ks(st0.copy(input = st0.input + s, complete = false)))
     )
 
diff --git a/modules/tests/src/test/scala/atto/CharacterTest.scala b/modules/tests/src/test/scala/atto/CharacterTest.scala
index 0d4ff45..ee73d64 100644
--- a/modules/tests/src/test/scala/atto/CharacterTest.scala
+++ b/modules/tests/src/test/scala/atto/CharacterTest.scala
@@ -94,8 +94,14 @@ object CharacterTest extends Properties("Character") {
       (if (predicate(c)) Some(()) else None)
   }
 
-  property("horizontalWhitespace") = forAll { (c: Char) =>
-    horizontalWhitespace.parseOnly(c.toString).option ===
-      (if (c == ' ' || c == '\t') Some(c) else None)
+  property("horizontalWhitespace") = forAll(Gen.oneOf(Generators.horizontalWhitespace, Arbitrary.arbitrary[Char])) { (c: Char) =>
+    //println(f"CHK(${c.toInt}%04x) TEST(${CharClass.horizontalWhitespace.unapplySeq(c).flatMap(_.headOption)}) PARSE(${horizontalWhitespace.parseOnly(c.toString).option})")
+    horizontalWhitespace.parseOnly(c.toString).option === CharClass.horizontalWhitespace.unapplySeq(c).flatMap(_.headOption)
   }
 }
+
+private object CharClass {
+  val horizontalWhitespace = raw"(\h)".r    // " \t\xA0\u1680\u180e\u2000-\u200a\u202f\u205f\u3000"
+  val horizontalWhitespaceChars =
+    " \u0009\u00A0\u1680\u180e\u202f\u205f\u3000".toVector ++ ('\u2000' to '\u200a').toVector
+}
diff --git a/modules/tests/src/test/scala/atto/Generators.scala b/modules/tests/src/test/scala/atto/Generators.scala
index 2dd75ad..b8f84ea 100644
--- a/modules/tests/src/test/scala/atto/Generators.scala
+++ b/modules/tests/src/test/scala/atto/Generators.scala
@@ -3,6 +3,7 @@ package atto
 import org.scalacheck.Gen
 
 object Generators {
-  val whitespace: Gen[Char] =
-    Gen.oneOf('\n', ' ', '\t')
+  val whitespace: Gen[Char] = Gen.oneOf('\n', ' ', '\t')
+
+  val horizontalWhitespace = Gen.oneOf(CharClass.horizontalWhitespaceChars)
 }
diff --git a/project/build.properties b/project/build.properties
index 88dc997..cc68b53 100644
--- a/project/build.properties
+++ b/project/build.properties
@@ -1 +1 @@
-sbt.version=1.5.8
\ No newline at end of file
+sbt.version=1.10.11
diff --git a/project/plugins.sbt b/project/plugins.sbt
index 02b6718..2663b5b 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -1,9 +1,9 @@
 addSbtPlugin("com.lightbend.paradox"     % "sbt-paradox"              % "0.9.2")
 addSbtPlugin("com.typesafe.sbt"          % "sbt-site"                 % "1.4.1")
 addSbtPlugin("com.typesafe.sbt"          % "sbt-ghpages"              % "0.6.3")
-addSbtPlugin("com.github.sbt"              % "sbt-ci-release"           % "1.5.10")
+addSbtPlugin("com.github.sbt"            % "sbt-ci-release"           % "1.5.10")
 addSbtPlugin("com.timushev.sbt"          % "sbt-updates"              % "0.5.3")
 addSbtPlugin("io.github.davidgregory084" % "sbt-tpolecat"             % "0.1.20")
 addSbtPlugin("org.portable-scala"        % "sbt-scalajs-crossproject" % "1.0.0")
-addSbtPlugin("org.scala-js"              % "sbt-scalajs"              % "1.5.1")
+addSbtPlugin("org.scala-js"              % "sbt-scalajs"              % "1.19.0")
 addSbtPlugin("org.scoverage"             % "sbt-scoverage"            % "1.6.1")