diff --git a/core/runtime.jvm/src/kotlin/reflect/jvm/internal/util.kt b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/util.kt
index cf150b786b3..420555dafb1 100644
--- a/core/runtime.jvm/src/kotlin/reflect/jvm/internal/util.kt
+++ b/core/runtime.jvm/src/kotlin/reflect/jvm/internal/util.kt
@@ -16,8 +16,9 @@
 
 package kotlin.reflect.jvm.internal
 
+import java.lang.ref.WeakReference
 import java.lang.reflect.Method
-import java.util.concurrent.ConcurrentHashMap
+import java.util.Arrays
 import kotlin.reflect.jvm.internal.pcollections.HashPMap
 
 // TODO: use stdlib?
@@ -47,15 +48,34 @@ private fun Class<*>.getMaybeDeclaredMethod(name: String, vararg parameterTypes:
 }
 
 
-// TODO: should use weak references
-private var foreignKClasses = HashPMap.empty<Class<*>, KClassImpl<*>>()!!
+// TODO: collect nulls periodically
+private var FOREIGN_K_CLASSES = HashPMap.empty<String, Array<WeakReference<KClassImpl<*>>>>()!!
 
 fun <T> foreignKotlinClass(jClass: Class<T>): KClassImpl<T> {
-    val cached = foreignKClasses[jClass] as? KClassImpl<T>
-    if (cached != null) return cached
-    val result = KClassImpl<T>(jClass)
-    foreignKClasses = foreignKClasses.plus(jClass, result)!!
-    return result
+    val name = jClass.getName()
+    val cached = FOREIGN_K_CLASSES[name]
+    if (cached != null) {
+        var i = cached.size - 1
+        while (i >= 0) {
+            val kClass = cached[i].get()
+            if (kClass?.jClass == jClass) {
+                return kClass as KClassImpl<T>
+            }
+            i--
+        }
+
+        val newArray = Arrays.copyOf(cached, cached.size + 1) as Array<WeakReference<KClassImpl<*>>>
+        val newKClass = KClassImpl<T>(jClass)
+        newArray[cached.size] = WeakReference(newKClass)
+        FOREIGN_K_CLASSES = FOREIGN_K_CLASSES.plus(name, newArray)!!
+        return newKClass
+    }
+
+    val newKClass = KClassImpl<T>(jClass)
+    val newArray = arrayOfNulls<WeakReference<KClassImpl<*>>>(1)
+    newArray[0] = WeakReference(newKClass)
+    FOREIGN_K_CLASSES = FOREIGN_K_CLASSES.plus(name, newArray as Array<WeakReference<KClassImpl<*>>>)!!
+    return newKClass
 }
 
 private val K_OBJECT_CLASS = Class.forName("kotlin.jvm.internal.KObject")