diff --git a/javascript/js-type-analysis/src/org/jetbrains/dukat/js/type/constraint/properties/ObjectConstraint.kt b/javascript/js-type-analysis/src/org/jetbrains/dukat/js/type/constraint/properties/ObjectConstraint.kt
index 9752c5c70..884924efa 100644
--- a/javascript/js-type-analysis/src/org/jetbrains/dukat/js/type/constraint/properties/ObjectConstraint.kt
+++ b/javascript/js-type-analysis/src/org/jetbrains/dukat/js/type/constraint/properties/ObjectConstraint.kt
@@ -9,7 +9,19 @@ class ObjectConstraint(
         val instantiatedClass: PropertyOwnerConstraint? = null
 ) : PropertyOwnerConstraint(owner) {
     val propertyNames: Set<String>
-        get() = properties.keys
+        get() {
+            val names = properties.keys.toMutableSet()
+
+            if (instantiatedClass is PropertyOwner) {
+                val classPrototype = instantiatedClass["prototype"]
+
+                if (classPrototype is ObjectConstraint) {
+                    names.addAll(classPrototype.propertyNames)
+                }
+            }
+
+            return names
+        }
 
     private val properties = LinkedHashMap<String, Constraint>()
 
diff --git a/javascript/js-type-analysis/src/org/jetbrains/dukat/js/type/constraint/resolution/constraintToDeclaration.kt b/javascript/js-type-analysis/src/org/jetbrains/dukat/js/type/constraint/resolution/constraintToDeclaration.kt
index c0008a69a..37cdb5ee0 100644
--- a/javascript/js-type-analysis/src/org/jetbrains/dukat/js/type/constraint/resolution/constraintToDeclaration.kt
+++ b/javascript/js-type-analysis/src/org/jetbrains/dukat/js/type/constraint/resolution/constraintToDeclaration.kt
@@ -188,14 +188,6 @@ private fun ObjectConstraint.mapMembers() : List<MemberDeclaration> {
             }
     )
 
-    if (instantiatedClass is PropertyOwner) {
-        val classPrototype = instantiatedClass["prototype"]
-
-        if (classPrototype is ObjectConstraint) {
-            members.addAll(classPrototype.mapMembers())
-        }
-    }
-
     return members
 }
 
diff --git a/typescript/ts-lowerings/src/org/jetbrains/dukat/tsLowerings/mergeDuplicates/mergeDuplicates.kt b/typescript/ts-lowerings/src/org/jetbrains/dukat/tsLowerings/mergeDuplicates/mergeDuplicates.kt
index 8000fb3cf..0b8644f81 100644
--- a/typescript/ts-lowerings/src/org/jetbrains/dukat/tsLowerings/mergeDuplicates/mergeDuplicates.kt
+++ b/typescript/ts-lowerings/src/org/jetbrains/dukat/tsLowerings/mergeDuplicates/mergeDuplicates.kt
@@ -9,6 +9,7 @@ import org.jetbrains.dukat.tsmodel.FunctionLikeDeclaration
 import org.jetbrains.dukat.tsmodel.MemberDeclaration
 import org.jetbrains.dukat.tsmodel.ModuleDeclaration
 import org.jetbrains.dukat.tsmodel.ParameterDeclaration
+import org.jetbrains.dukat.tsmodel.PropertyDeclaration
 import org.jetbrains.dukat.tsmodel.SourceFileDeclaration
 import org.jetbrains.dukat.tsmodel.SourceSetDeclaration
 import org.jetbrains.dukat.tsmodel.TopLevelDeclaration
@@ -133,6 +134,7 @@ private fun List<MemberDeclaration>.mergeMembers() : List<MemberDeclaration> {
             is ConstructorDeclaration -> constructors += member.mergeDuplicates()
             is FunctionDeclaration -> methods += member.mergeDuplicates()
             is CallSignatureDeclaration -> callSignatures += member.mergeDuplicates()
+            is PropertyDeclaration -> otherMembers += member.mergeDuplicates()
             else -> otherMembers += member
         }
     }
@@ -151,6 +153,10 @@ private fun ParameterDeclaration.mergeDuplicates() = copy(
         type = type.mergeDuplicates()
 )
 
+private fun PropertyDeclaration.mergeDuplicates() = copy(
+        type = type.mergeDuplicates()
+)
+
 private fun ConstructorDeclaration.mergeDuplicates() = copy(
         parameters = parameters.map { it.mergeDuplicates() }
 )
diff --git a/typescript/ts-lowerings/src/org/jetbrains/dukat/tsLowerings/mergeDuplicates/normalize.kt b/typescript/ts-lowerings/src/org/jetbrains/dukat/tsLowerings/mergeDuplicates/normalize.kt
index cc8ad4794..9ed44b994 100644
--- a/typescript/ts-lowerings/src/org/jetbrains/dukat/tsLowerings/mergeDuplicates/normalize.kt
+++ b/typescript/ts-lowerings/src/org/jetbrains/dukat/tsLowerings/mergeDuplicates/normalize.kt
@@ -5,6 +5,7 @@ import org.jetbrains.dukat.tsmodel.ConstructorDeclaration
 import org.jetbrains.dukat.tsmodel.FunctionDeclaration
 import org.jetbrains.dukat.tsmodel.MemberDeclaration
 import org.jetbrains.dukat.tsmodel.ParameterDeclaration
+import org.jetbrains.dukat.tsmodel.PropertyDeclaration
 import org.jetbrains.dukat.tsmodel.types.FunctionTypeDeclaration
 import org.jetbrains.dukat.tsmodel.types.ObjectLiteralDeclaration
 import org.jetbrains.dukat.tsmodel.types.ParameterValueDeclaration
@@ -31,6 +32,7 @@ internal fun MemberDeclaration.normalize(): MemberDeclaration {
         is CallSignatureDeclaration -> this.normalize()
         is ConstructorDeclaration -> this.normalize()
         is FunctionDeclaration -> this.normalize()
+        is PropertyDeclaration -> this.normalize()
         else -> this
     }
 }
@@ -47,6 +49,10 @@ internal fun FunctionDeclaration.normalize(substituteType: ParameterValueDeclara
         uid = IRRELEVANT_UID
 )
 
+internal fun PropertyDeclaration.normalize() = copy(
+        type = type.normalize()
+)
+
 internal fun UnionTypeDeclaration.normalize() = copy(
         params = params.map { it.normalize() }
 )