diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala b/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
index 7c126e3d2cb4..5a4f83a92b0f 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala
@@ -33,7 +33,7 @@ abstract class BCodeBodyBuilder extends BCodeSkelBuilder {
   import bTypes._
   import coreBTypes._
   import definitions._
-  import genBCode.postProcessor.backendUtils.addIndyLambdaImplMethod
+  import genBCode.postProcessor.backendUtils.{addIndyLambdaImplMethod, classfileVersion}
   import genBCode.postProcessor.callGraph.{inlineAnnotatedCallsites, noInlineAnnotatedCallsites}
 
   /*
@@ -991,7 +991,11 @@ abstract class BCodeBodyBuilder extends BCodeSkelBuilder {
       }
     }
 
-    /* Generate string concatenation code based on the strategy specified at `-YstringConcat` */
+    /* Generate string concatenation
+     *
+     * On JDK 8: create and append using `StringBuilder`
+     * On JDK 9+: use `invokedynamic` with `StringConcatFactory`
+     */
     def genStringConcat(tree: Tree): BType = {
       lineNumber(tree)
       liftStringConcat(tree) match {
@@ -1016,8 +1020,8 @@ abstract class BCodeBodyBuilder extends BCodeSkelBuilder {
             }
             .toList
 
-          if (currentSettings.YstringConcat.value == "inline" ||
-              currentSettings.YstringConcat.value == "detect" && currentSettings.target.value == "8") {
+          // `StringConcatFactory` only got added in JDK 9, so use `StringBuilder` for lower
+          if (classfileVersion.get < asm.Opcodes.V9) {
 
             // Estimate capacity needed for the string builder
             val approxBuilderSize = concatArguments.view.map {
diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index 8df8fe5c70a1..d070a7870652 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -278,7 +278,6 @@ trait ScalaSettings extends StandardScalaSettings with Warnings { _: MutableSett
 
   val exposeEmptyPackage = BooleanSetting ("-Yexpose-empty-package", "Internal only: expose the empty package.").internalOnly()
   val Ydelambdafy        = ChoiceSetting  ("-Ydelambdafy", "strategy", "Strategy used for translating lambdas into JVM code.", List("inline", "method"), "method")
-  val YstringConcat      = ChoiceSetting  ("-YstringConcat", "strategy", "Strategy used for translating string concatenation into JVM code.", List("inline", "indy", "detect"), "detect")
 
   // Allows a specialised jar to be written. For instance one that provides stable hashing of content, or customisation of the file storage
   val YjarFactory = StringSetting   ("-YjarFactory", "classname", "factory for jar files", classOf[DefaultJarFactory].getName)