diff --git a/compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala b/compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala
index 27949f3fb899..91d6b2c7fbf2 100644
--- a/compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala
+++ b/compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala
@@ -484,6 +484,7 @@ trait ConstraintHandling {
    *  way isSubType is organized.
    */
   protected def addConstraint(param: TypeParamRef, bound: Type, fromBelow: Boolean)(using Context): Boolean =
+    if !bound.isValueTypeOrLambda then return false
 
     /** When comparing lambdas we might get constraints such as
      *  `A <: X0` or `A = List[X0]` where `A` is a constrained parameter