diff --git a/.github/workflows/scala.yml b/.github/workflows/scala.yml
index b71dce1..a5d7005 100644
--- a/.github/workflows/scala.yml
+++ b/.github/workflows/scala.yml
@@ -4,6 +4,7 @@ on: [push]
 
 jobs:
   UnitTests:
+
     runs-on: ubuntu-latest
 
     steps:
@@ -28,6 +29,7 @@ jobs:
       run: sbt test
 
   MutationTests:
+
     runs-on: ubuntu-latest
 
     steps:
diff --git a/.travis.yml b/.travis.yml
index 53b5661..ec962ca 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,6 @@
 language: scala
 scala:
+  - 2.13.1
   - 2.12.8
 
 before_cache:
diff --git a/build.sbt b/build.sbt
index 5944bc0..fbc6be2 100644
--- a/build.sbt
+++ b/build.sbt
@@ -1,6 +1,6 @@
 name := "mathimatica-parser"
 
-scalaVersion := "2.12.8"
+scalaVersion := "2.13.1"
 
 libraryDependencies += "org.scala-lang.modules"     %% "scala-parser-combinators" % "1.1.2"
 libraryDependencies += "com.typesafe.scala-logging" %% "scala-logging"            % "3.9.2"
@@ -10,6 +10,8 @@ libraryDependencies += "org.scalatest"     %% "scalatest"                % "3.1.
 libraryDependencies += "org.scalacheck"    %% "scalacheck"               % "1.14.2"      % Test
 libraryDependencies += "org.scalatestplus" %% "scalatestplus-scalacheck" % "3.1.0.0-RC2" % Test
 
+scalacOptions ++= Seq("-deprecation")
+
 // POM settings for Sonatype
 organization := "com.github.tomerghelber"
 homepage := Some(
diff --git a/project/safety.sbt b/project/safety.sbt
index f476b72..fff9b42 100644
--- a/project/safety.sbt
+++ b/project/safety.sbt
@@ -1 +1 @@
-addSbtPlugin("com.leobenkel" % "safety_plugin" % "0.1.4")
+addSbtPlugin("com.leobenkel" % "safety_plugin" % "0.1.5")
diff --git a/safetyPlugin.json b/safetyPlugin.json
index 534b9ea..fe7dbe3 100644
--- a/safetyPlugin.json
+++ b/safetyPlugin.json
@@ -1,6 +1,8 @@
 {
   "sbtVersion": "1.3.4",
   "scalaVersions": [
+    "2.13.1",
+    "2.13.0",
     "2.12.8"
   ],
   "modules": {
diff --git a/src/main/scala/com/github/tomerghelber/mathematica/normalform/NormalForm.scala b/src/main/scala/com/github/tomerghelber/mathematica/normalform/NormalForm.scala
index d8cc4cc..28a5ea9 100644
--- a/src/main/scala/com/github/tomerghelber/mathematica/normalform/NormalForm.scala
+++ b/src/main/scala/com/github/tomerghelber/mathematica/normalform/NormalForm.scala
@@ -77,7 +77,7 @@ object NormalForm {
     }
     private val normalFormFunctionNodeOrdering = {
       val functionNameOrdering = TerminalNodeOrdering.on[FunctionNode](_.name)
-      val functionArgumentsOrdering = Ordering.Iterable(ASTNodeOrdering).on[FunctionNode](_.arguments)
+      val functionArgumentsOrdering = Ordering.Implicits.seqOrdering(ASTNodeOrdering).on[FunctionNode](_.arguments)
       functionNameOrdering thenComparing functionArgumentsOrdering
     }
   }
diff --git a/src/test/scala/com/github/tomerghelber/mathematica/package.scala b/src/test/scala/com/github/tomerghelber/mathematica/package.scala
index f022b63..c5ac670 100644
--- a/src/test/scala/com/github/tomerghelber/mathematica/package.scala
+++ b/src/test/scala/com/github/tomerghelber/mathematica/package.scala
@@ -24,11 +24,11 @@ package object mathematica {
     .map(_.replaceAll("\\\\", "\\\\")
       .replaceAll("\"", "\\\""))
   val stringStringGen: Gen[String] = stringWithoutWrappersGen.map(s => "\"" + s + "\"")
-  val symbolStringGen: Gen[String] = for (head <- Gen.alphaChar; last <- Gen.alphaNumStr) yield { head + last }
+  val symbolStringGen: Gen[String] = for (head <- Gen.alphaChar; last <- Gen.alphaNumStr) yield { s"$head$last" }
   private val integerGen: Gen[Int] = Gen.chooseNum(Int.MinValue, Int.MaxValue)
   private val longGen: Gen[Long] = Gen.chooseNum(Long.MinValue, Long.MaxValue)
   val integerStringGen: Gen[String] = longGen.map(_.toString)
-  val rationalStringGen: Gen[String] = for(q <-longGen; p <-longGen if p != 0) yield { q + "/" + p}
+  val rationalStringGen: Gen[String] = for(q <-longGen; p <-longGen if p != 0) yield { s"$q/$p" }
   val floatStringGen: Gen[String] = Gen.chooseNum(Double.MinValue, Double.MaxValue).map(_.toString)
   val scientificNotationGen: Gen[String] = Gen.chooseNum(Double.MinValue, Double.MaxValue).map(BigDecimal(_).toString)
   val numberStringGen: Gen[String] = Gen.oneOf(integerStringGen, rationalStringGen, floatStringGen,