diff --git a/compiler/fir/fir2ir/jvm-backend/src/org/jetbrains/kotlin/fir/backend/jvm/FirJvmMangleComputer.kt b/compiler/fir/fir2ir/jvm-backend/src/org/jetbrains/kotlin/fir/backend/jvm/FirJvmMangleComputer.kt
index e96e915718d..a358f3857cc 100644
--- a/compiler/fir/fir2ir/jvm-backend/src/org/jetbrains/kotlin/fir/backend/jvm/FirJvmMangleComputer.kt
+++ b/compiler/fir/fir2ir/jvm-backend/src/org/jetbrains/kotlin/fir/backend/jvm/FirJvmMangleComputer.kt
@@ -255,10 +255,23 @@ open class FirJvmMangleComputer(
                     tBuilder.appendSignature(MangleConstant.ENHANCED_NULLABILITY_MARK)
                 }
             }
+            is ConeRawType -> {
+                mangleType(tBuilder, type.lowerBound)
+            }
             is ConeFlexibleType -> {
-                // Need to reproduce type approximation done for flexible types in TypeTranslator.
-                // For now, we replicate the current behaviour of Fir2IrTypeConverter and just take the upper bound
-                mangleType(tBuilder, type.upperBound)
+                with(session.typeContext) {
+                    // Need to reproduce type approximation done for flexible types in TypeTranslator.
+                    // For now, we replicate the current behaviour of Fir2IrTypeConverter and just take the upper bound
+                    val upper = type.upperBound
+                    if (upper is ConeClassLikeType) {
+                        val lower = type.lowerBound as? ConeClassLikeType ?: error("Expecting class-like type, got ${type.lowerBound}")
+                        val intermediate = if (lower.lookupTag == upper.lookupTag) {
+                            lower.replaceArguments(upper.getArguments())
+                        } else lower
+                        val mixed = if (upper.isNullable) intermediate.makeNullable() else intermediate.makeDefinitelyNotNullOrNotNull()
+                        mangleType(tBuilder, mixed as ConeKotlinType)
+                    } else mangleType(tBuilder, upper)
+                }
             }
             is ConeDefinitelyNotNullType -> {
                 // E.g. not-null type parameter in Java
diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrTypeConverter.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrTypeConverter.kt
index a25480c4e4f..fb3acf96fb1 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrTypeConverter.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrTypeConverter.kt
@@ -163,13 +163,26 @@ class Fir2IrTypeConverter(
                 // (some reflection tests rely on this)
                 lowerBound.toIrType(
                     typeContext,
+                    annotations,
                     hasFlexibleNullability = lowerBound.nullability != upperBound.nullability,
                     addRawTypeAnnotation = true
                 )
             }
-            is ConeFlexibleType -> {
-                // TODO: yet we take more general type. Not quite sure it's Ok
-                upperBound.toIrType(typeContext, hasFlexibleNullability = lowerBound.nullability != upperBound.nullability)
+            is ConeFlexibleType -> with(session.typeContext) {
+                if (upperBound is ConeClassLikeType) {
+                    val upper = upperBound as ConeClassLikeType
+                    val lower = lowerBound as? ConeClassLikeType ?: error("Expecting class-like type, got $lowerBound")
+                    val intermediate = if (lower.lookupTag == upper.lookupTag) {
+                        lower.replaceArguments(upper.getArguments())
+                    } else lower
+                    (intermediate.withNullability(upper.isNullable) as ConeKotlinType)
+                        .withAttributes(lower.attributes)
+                        .toIrType(
+                            typeContext, annotations, hasFlexibleNullability = lower.nullability != upper.nullability
+                        )
+                } else {
+                    upperBound.toIrType(typeContext, annotations, hasFlexibleNullability = lowerBound.nullability != upperBound.nullability)
+                }
             }
             is ConeCapturedType -> {
                 val cached = capturedTypeCache[this]