diff --git a/testcases/verification/strings/invalid/CompatibleListChar.scala b/testcases/verification/strings/invalid/CompatibleListChar.scala
new file mode 100644
index 0000000000000000000000000000000000000000..86eec34cddcee8055c34d5ffc791b7bbf7a397e7
--- /dev/null
+++ b/testcases/verification/strings/invalid/CompatibleListChar.scala
@@ -0,0 +1,29 @@
+import leon.lang._
+import leon.annotation._
+import leon.collection._
+import leon.collection.ListOps._
+import leon.lang.synthesis._
+
+object CompatibleListChar {
+  def rec[T](l : List[T], f : T => String): String = l match {
+	case Cons(head, tail) => f(head) + rec(tail, f)
+	case Nil() => ""
+  }
+  def customToString[T](l : List[T], p: List[Char], d: String, fd: String => String, fp: List[Char] => String, pf: String => List[Char], f : T => String): String =  rec(l, f) ensuring {
+    (res : String) => (p == Nil[Char]() || d == "" || fd(d) == "" || fp(p) == "" || pf(d) == Nil[Char]()) && ((l, res) passes {
+      case Cons(a, Nil()) => f(a)
+    })
+  }
+  def customPatternMatching(s: String): Boolean = {
+    s match {
+	  case "" => true
+	  case b => List(b) match {
+	    case Cons("", Nil()) => true
+	    case Cons(s, Nil()) => false // StrOps.length(s) < BigInt(2) // || (s == "\u0000") //+ "a"
+		case Cons(_, Cons(_, Nil())) => true
+		case _ => false
+	  }
+	  case _ => false
+	}
+  } holds
+}
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