diff --git a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
index 09f826c1b154..2a6df10a76de 100644
--- a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
@@ -480,7 +480,8 @@ object SymDenotations {
           // duplicate scalac's behavior: don't write a double '$$' for module class members.
           prefix = prefix.exclude(ModuleClassName)
         def qualify(n: SimpleName) =
-          kind(prefix.toTermName, if (filler.isEmpty) n else termName(filler + n))
+          val qn = kind(prefix.toTermName, if (filler.isEmpty) n else termName(filler + n))
+          if kind == FlatName && !encl.is(JavaDefined) then qn.compactified else qn
         val fn = name replace {
           case name: SimpleName => qualify(name)
           case name @ AnyQualifiedName(_, _) => qualify(name.mangled.toSimpleName)
diff --git a/sbt-dotty/sbt-test/scala2-compat/longnames/build.sbt b/sbt-dotty/sbt-test/scala2-compat/longnames/build.sbt
new file mode 100644
index 000000000000..67bfb8edb65f
--- /dev/null
+++ b/sbt-dotty/sbt-test/scala2-compat/longnames/build.sbt
@@ -0,0 +1,9 @@
+val scala3Version = sys.props("plugin.scalaVersion")
+val scala2Version = "2.13.4"
+
+lazy val lib = (project in file ("lib"))
+  .settings(scalaVersion := scala2Version)
+
+lazy val test = (project in file ("main"))
+  .dependsOn(lib)
+  .settings(scalaVersion := scala3Version)
diff --git a/sbt-dotty/sbt-test/scala2-compat/longnames/lib/lib.scala b/sbt-dotty/sbt-test/scala2-compat/longnames/lib/lib.scala
new file mode 100644
index 000000000000..00a14043278b
--- /dev/null
+++ b/sbt-dotty/sbt-test/scala2-compat/longnames/lib/lib.scala
@@ -0,0 +1,35 @@
+class reallongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongname {
+  object obj0
+  object obj01
+  object obj012
+  object obj0123
+  object obj01234
+  object obj012345
+  object obj0123456
+  object obj01234567
+  object obj012345678
+  object obj0123456789
+  object obj01234567890
+  class cls0
+  class cls01
+  class cls012
+  class cls0123
+  class cls01234
+  class cls012345
+  class cls0123456
+  class cls01234567
+  class cls012345678
+  class cls0123456789
+  class cls01234567890
+  trait trt0
+  trait trt01
+  trait trt012
+  trait trt0123
+  trait trt01234
+  trait trt012345
+  trait trt0123456
+  trait trt01234567
+  trait trt012345678
+  trait trt0123456789
+  trait trt01234567890
+}
diff --git a/sbt-dotty/sbt-test/scala2-compat/longnames/main/test.scala b/sbt-dotty/sbt-test/scala2-compat/longnames/main/test.scala
new file mode 100644
index 000000000000..4a5ee58a8125
--- /dev/null
+++ b/sbt-dotty/sbt-test/scala2-compat/longnames/main/test.scala
@@ -0,0 +1,41 @@
+object Test extends App {
+  val c = new reallongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongnamereallylongname
+
+  import c._
+
+  val o0 = obj0
+  val o1 = obj01
+  val o2 = obj012
+  val o3 = obj0123
+  val o4 = obj01234
+  val o5 = obj012345
+  val o6 = obj0123456
+  val o7 = obj01234567
+  val o8 = obj012345678
+  val o9 = obj0123456789
+  val o10 = obj01234567890
+
+  val c0 = new cls0
+  val c1 = new cls01
+  val c2 = new cls012
+  val c3 = new cls0123
+  val c4 = new cls01234
+  val c5 = new cls012345
+  val c6 = new cls0123456
+  val c7 = new cls01234567
+  val c8 = new cls012345678
+  val c9 = new cls0123456789
+  val c10 = new cls01234567890
+
+  val t0 = new trt0 {}
+  val t1 = new trt01 {}
+  val t2 = new trt012 {}
+  val t3 = new trt0123 {}
+  val t4 = new trt01234 {}
+  val t5 = new trt012345 {}
+  val t6 = new trt0123456 {}
+  val t7 = new trt01234567 {}
+  val t8 = new trt012345678 {}
+  val t9 = new trt0123456789 {}
+  val t10 = new trt01234567890 {}
+}
diff --git a/sbt-dotty/sbt-test/scala2-compat/longnames/project/plugins.sbt b/sbt-dotty/sbt-test/scala2-compat/longnames/project/plugins.sbt
new file mode 100644
index 000000000000..c17caab2d98c
--- /dev/null
+++ b/sbt-dotty/sbt-test/scala2-compat/longnames/project/plugins.sbt
@@ -0,0 +1 @@
+addSbtPlugin("ch.epfl.lamp" % "sbt-dotty" % sys.props("plugin.version"))
diff --git a/sbt-dotty/sbt-test/scala2-compat/longnames/test b/sbt-dotty/sbt-test/scala2-compat/longnames/test
new file mode 100644
index 000000000000..8aedcd64cf5b
--- /dev/null
+++ b/sbt-dotty/sbt-test/scala2-compat/longnames/test
@@ -0,0 +1 @@
+> test/run
diff --git a/tests/run/java-longnames/Long_1.java b/tests/run/java-longnames/Long_1.java
new file mode 100644
index 000000000000..7c449a489358
--- /dev/null
+++ b/tests/run/java-longnames/Long_1.java
@@ -0,0 +1,6 @@
+package p;
+
+public class Long_1 {
+    public static class ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ_1 {
+    }
+}
diff --git a/tests/run/java-longnames/Test_2.scala b/tests/run/java-longnames/Test_2.scala
new file mode 100644
index 000000000000..b03954825173
--- /dev/null
+++ b/tests/run/java-longnames/Test_2.scala
@@ -0,0 +1,9 @@
+import p._
+
+object Test extends App {
+  println(
+    new Long_1.ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ_1()
+      .getClass
+      .getName
+  )
+}
diff --git a/tests/pending/run/t8199.scala b/tests/run/t8199.scala
similarity index 98%
rename from tests/pending/run/t8199.scala
rename to tests/run/t8199.scala
index afd417ffd23f..ffd847ef3787 100644
--- a/tests/pending/run/t8199.scala
+++ b/tests/run/t8199.scala
@@ -44,7 +44,6 @@ object Test extends App {
   }
   def checkCallerImplClassName(): Unit = {
     val name = Thread.currentThread.getStackTrace.apply(2).getClassName
-    assert(name.contains("$class"))
     Test.checkClassName(name)
   }