diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/descriptors/LazyClassMemberScope.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/descriptors/LazyClassMemberScope.kt
index 56da54970f8..54c9269fbaa 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/descriptors/LazyClassMemberScope.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/descriptors/LazyClassMemberScope.kt
@@ -134,8 +134,7 @@ public open class LazyClassMemberScope(
     private fun generateDataClassMethods(result: MutableCollection<FunctionDescriptor>, name: Name) {
         if (!KotlinBuiltIns.isData(thisDescriptor)) return
 
-        val constructor = getPrimaryConstructor()
-        if (constructor == null) return
+        val constructor = getPrimaryConstructor() ?: return
 
         val primaryConstructorParameters = declarationProvider.getOwnerInfo().getPrimaryConstructorParameters()
         assert(constructor.getValueParameters().size() == primaryConstructorParameters.size()) { "From descriptor: " + constructor.getValueParameters().size() + " but from PSI: " + primaryConstructorParameters.size() }
@@ -150,8 +149,6 @@ public open class LazyClassMemberScope(
                 val properties = getProperties(parameter.getName())
                 if (properties.isEmpty()) continue
 
-                assert(properties.size() == 1) { "A constructor parameter is resolved to more than one (" + properties.size() + ") property: " + parameter }
-
                 val property = properties.iterator().next() as PropertyDescriptor
 
                 ++componentIndex
diff --git a/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.kt b/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.kt
new file mode 100644
index 00000000000..75cc614787b
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.kt
@@ -0,0 +1,9 @@
+data class A1(val <!REDECLARATION, REDECLARATION, REDECLARATION!>x<!>: Int, val y: String, val <!REDECLARATION, REDECLARATION, REDECLARATION!>x<!>: Int) {
+    val z = ""
+}
+
+data class A2(val <!REDECLARATION!>x<!>: Int, val y: String) {
+    val <!REDECLARATION!>x<!> = ""
+}
+
+data class A3(<!REDECLARATION, REDECLARATION, REDECLARATION!>val<!SYNTAX!><!> :Int<!>, <!REDECLARATION, REDECLARATION, REDECLARATION!>val<!SYNTAX!><!> : Int<!>)
diff --git a/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.txt b/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.txt
new file mode 100644
index 00000000000..218a8267bdc
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.txt
@@ -0,0 +1,41 @@
+package 
+
+kotlin.data() internal final class A1 {
+    public constructor A1(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.String, /*2*/ x: kotlin.Int)
+    internal final val x: kotlin.Int
+    internal final val x: kotlin.Int
+    internal final val y: kotlin.String
+    internal final val z: kotlin.String = ""
+    internal final /*synthesized*/ fun component1(): kotlin.Int
+    internal final /*synthesized*/ fun component2(): kotlin.String
+    internal final /*synthesized*/ fun component3(): kotlin.Int
+    public final /*synthesized*/ fun copy(/*0*/ x: kotlin.Int = ..., /*1*/ y: kotlin.String = ..., /*2*/ x: kotlin.Int = ...): A1
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+kotlin.data() internal final class A2 {
+    public constructor A2(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.String)
+    internal final val x: kotlin.Int
+    internal final val x: kotlin.String = ""
+    internal final val y: kotlin.String
+    internal final /*synthesized*/ fun component1(): kotlin.String
+    internal final /*synthesized*/ fun component2(): kotlin.String
+    public final /*synthesized*/ fun copy(/*0*/ x: kotlin.Int = ..., /*1*/ y: kotlin.String = ...): A2
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+kotlin.data() internal final class A3 {
+    public constructor A3(/*0*/ <no name provided>: kotlin.Int, /*1*/ <no name provided>: kotlin.Int)
+    internal final val <no name provided>: kotlin.Int
+    internal final val <no name provided>: kotlin.Int
+    internal final /*synthesized*/ fun component1(): kotlin.Int
+    internal final /*synthesized*/ fun component2(): kotlin.Int
+    public final /*synthesized*/ fun copy(/*0*/ <no name provided>: kotlin.Int = ..., /*1*/ <no name provided>: kotlin.Int = ...): A3
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestGenerated.java
index 18ef31fa22f..6bc2bb70aa9 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestGenerated.java
@@ -2844,6 +2844,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("repeatedProperties.kt")
+            public void testRepeatedProperties() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("secondParamIsVal.kt")
             public void testSecondParamIsVal() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/dataClasses/secondParamIsVal.kt");