diff --git a/scalafix/2.13/input/src/main/scala/fix/Collectionstrawman_v0_copyToBuffer.scala b/scalafix/2.13/input/src/main/scala/fix/Collectionstrawman_v0_copyToBuffer.scala
new file mode 100644
index 0000000000..a75c4fbeb7
--- /dev/null
+++ b/scalafix/2.13/input/src/main/scala/fix/Collectionstrawman_v0_copyToBuffer.scala
@@ -0,0 +1,13 @@
+/*
+rule = "scala:fix.Collectionstrawman_v0"
+ */
+package fix
+
+import scala.collection.mutable
+
+class Collectionstrawman_v0_copyToBuffer(xs: List[Int], b: mutable.Buffer[Int]) {
+
+  xs.copyToBuffer(b)
+  (xs ++ xs).copyToBuffer(b)
+
+}
diff --git a/scalafix/2.13/output/src/main/scala/fix/Collectionstrawman_v0_copyToBuffer.scala b/scalafix/2.13/output/src/main/scala/fix/Collectionstrawman_v0_copyToBuffer.scala
new file mode 100644
index 0000000000..8615a47af8
--- /dev/null
+++ b/scalafix/2.13/output/src/main/scala/fix/Collectionstrawman_v0_copyToBuffer.scala
@@ -0,0 +1,10 @@
+package fix
+
+import scala.collection.mutable
+
+class Collectionstrawman_v0_copyToBuffer(xs: List[Int], b: mutable.Buffer[Int]) {
+
+  b ++= xs
+  b ++= xs ++ xs
+
+}
diff --git a/scalafix/2.13/rules/src/main/scala/fix/Collectionstrawman_v0.scala b/scalafix/2.13/rules/src/main/scala/fix/Collectionstrawman_v0.scala
index 17204f058c..191c6beade 100644
--- a/scalafix/2.13/rules/src/main/scala/fix/Collectionstrawman_v0.scala
+++ b/scalafix/2.13/rules/src/main/scala/fix/Collectionstrawman_v0.scala
@@ -86,9 +86,20 @@ case class Collectionstrawman_v0(index: SemanticdbIndex)
         removeTokensPatch + replaceCommasPatch
     }.asPatch
 
+  val copyToBuffer = SymbolMatcher.normalized(
+    Symbol("_root_.scala.collection.TraversableOnce.copyToBuffer.")
+  )
+
+  def replaceCopyToBuffer(ctx: RuleCtx): Patch =
+    ctx.tree.collect {
+      case t @ q"${copyToBuffer(Term.Select(collection, _))}($buffer)" =>
+        ctx.replaceTree(t, q"$buffer ++= $collection".syntax)
+    }.asPatch
+
   override def fix(ctx: RuleCtx): Patch = {
     replaceToList(ctx) +
       replaceSymbols(ctx) +
-      replaceTupleZipped(ctx)
+      replaceTupleZipped(ctx) +
+      replaceCopyToBuffer(ctx)
   }
 }
diff --git a/scalafix/2.13/tests/src/test/scala/fix/Collectionstrawman_Tests.scala b/scalafix/2.13/tests/src/test/scala/fix/Collectionstrawman_Tests.scala
index 023382b63b..83e8edb824 100644
--- a/scalafix/2.13/tests/src/test/scala/fix/Collectionstrawman_Tests.scala
+++ b/scalafix/2.13/tests/src/test/scala/fix/Collectionstrawman_Tests.scala
@@ -11,7 +11,6 @@ class Collectionstrawman_Tests
     Seq(AbsolutePath(BuildInfo.outputSourceroot))
   ) {
   override def assertNoDiff(a: String, b: String, c: String) = {
-    println(a)
     super.assertNoDiff(a, b, c)
   }
   runAllTests()