diff --git a/j2k/newSrc/org/jetbrains/kotlin/j2k/ConversionsRunner.kt b/j2k/newSrc/org/jetbrains/kotlin/j2k/ConversionsRunner.kt
index 7e05396130b..2e27961d17b 100644
--- a/j2k/newSrc/org/jetbrains/kotlin/j2k/ConversionsRunner.kt
+++ b/j2k/newSrc/org/jetbrains/kotlin/j2k/ConversionsRunner.kt
@@ -56,6 +56,7 @@ object ConversionsRunner {
             +ForInConversion()
             +CollectionOperationsConversion(context)
             +ArrayOperationsConversion(context)
+            +LowerNullabilityInFunctionParametersConversion(context)
             +TypeMappingConversion(context)
 
             //Kotlin --> Kotlin conversions
diff --git a/j2k/newSrc/org/jetbrains/kotlin/j2k/conversions/LowerNullabilityInFunctionParametersConversion.kt b/j2k/newSrc/org/jetbrains/kotlin/j2k/conversions/LowerNullabilityInFunctionParametersConversion.kt
new file mode 100644
index 00000000000..0ba5415c637
--- /dev/null
+++ b/j2k/newSrc/org/jetbrains/kotlin/j2k/conversions/LowerNullabilityInFunctionParametersConversion.kt
@@ -0,0 +1,55 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.j2k.conversions
+
+import org.jetbrains.kotlin.builtins.KotlinBuiltIns
+import org.jetbrains.kotlin.j2k.ConversionContext
+import org.jetbrains.kotlin.j2k.ast.Nullability
+import org.jetbrains.kotlin.j2k.tree.*
+import org.jetbrains.kotlin.j2k.tree.impl.*
+import org.jetbrains.kotlin.name.ClassId
+
+class LowerNullabilityInFunctionParametersConversion(private val context: ConversionContext) : RecursiveApplicableConversionBase() {
+    override fun applyToElement(element: JKTreeElement): JKTreeElement {
+        if (element !is JKMethod) return recurse(element)
+        val scopes =
+            listOfNotNull(
+                element.block,
+                (element as? JKKtConstructor)?.delegationCall
+            )
+        for (parameter in element.parameters) {
+            if (parameter.type.type.nullability == Nullability.NotNull) continue
+            if (parameter.hasNotNullUsages(scopes)) {
+                parameter.type = JKTypeElementImpl(parameter.type.type.updateNullability(Nullability.NotNull))
+            }
+        }
+        return recurse(element)
+    }
+
+    private fun JKParameter.hasNotNullUsages(scopes: List<JKTreeElement>): Boolean =
+        scopes.any {
+            val searcher = HasNotNullUsagesSearcher(context.symbolProvider.provideUniverseSymbol(this))
+            scopes.any { searcher.runConversion(it, context) }
+            searcher.found
+        }
+
+    private inner class HasNotNullUsagesSearcher(private val parameterSymbol: JKFieldSymbol) : RecursiveApplicableConversionBase() {
+        var found: Boolean = false
+        override fun applyToElement(element: JKTreeElement): JKTreeElement {
+            when (element) {
+                is JKQualifiedExpression -> {
+                    val receiver = element.receiver as? JKFieldAccessExpression ?: return recurse(element)
+                    if (receiver.identifier == parameterSymbol) {
+                        found = true
+                        return element
+                    }
+                }
+            }
+            return recurse(element)
+        }
+    }
+
+}
\ No newline at end of file