diff --git a/core/descriptors/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintSystemImpl.java b/core/descriptors/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintSystemImpl.java
index 640b4e05b35..0d5fb1fc1e6 100644
--- a/core/descriptors/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintSystemImpl.java
+++ b/core/descriptors/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintSystemImpl.java
@@ -423,8 +423,8 @@ public class ConstraintSystemImpl implements ConstraintSystem {
         //   Foo >: T!
         // both Foo and Foo? transform to Foo! here
         if (TypesPackage.isFlexible(parameterType)) {
-            CustomTypeVariable typeVariable = parameterType.getCapability(CustomTypeVariable.class);
-            if (typeVariable != null && typeVariable.getIsTypeVariable()) {
+            CustomTypeVariable typeVariable = TypesPackage.getCustomTypeVariable(parameterType);
+            if (typeVariable != null) {
                 constrainingType = typeVariable.substitutionResult(constrainingType);
             }
         }
diff --git a/core/descriptors/src/org/jetbrains/jet/lang/types/TypeCapabilities.kt b/core/descriptors/src/org/jetbrains/jet/lang/types/TypeCapabilities.kt
index fbefc322258..65d81aa9903 100644
--- a/core/descriptors/src/org/jetbrains/jet/lang/types/TypeCapabilities.kt
+++ b/core/descriptors/src/org/jetbrains/jet/lang/types/TypeCapabilities.kt
@@ -46,4 +46,8 @@ public trait CustomTypeVariable : TypeCapability {
     public fun substitutionResult(replacement: JetType): JetType
 }
 
-public fun JetType.isCustomTypeVariable(): Boolean = this.getCapability(javaClass<CustomTypeVariable>())?.isTypeVariable ?: false
\ No newline at end of file
+public fun JetType.isCustomTypeVariable(): Boolean = this.getCapability(javaClass<CustomTypeVariable>())?.isTypeVariable ?: false
+public fun JetType.getCustomTypeVariable(): CustomTypeVariable? =
+        this.getCapability(javaClass<CustomTypeVariable>())?.let {
+            if (it.isTypeVariable) it else null
+        }
\ No newline at end of file
diff --git a/core/descriptors/src/org/jetbrains/jet/lang/types/TypeSubstitutor.java b/core/descriptors/src/org/jetbrains/jet/lang/types/TypeSubstitutor.java
index eb7c39f4c22..122b07f33c7 100644
--- a/core/descriptors/src/org/jetbrains/jet/lang/types/TypeSubstitutor.java
+++ b/core/descriptors/src/org/jetbrains/jet/lang/types/TypeSubstitutor.java
@@ -187,9 +187,8 @@ public class TypeSubstitutor {
                     return TypeUtils.makeStarProjection(typeParameter);
                 case NO_CONFLICT:
                     JetType substitutedType;
-                    if (TypesPackage.isCustomTypeVariable(type)) {
-                        CustomTypeVariable typeVariable = type.getCapability(CustomTypeVariable.class);
-                        assert typeVariable != null;
+                    CustomTypeVariable typeVariable = TypesPackage.getCustomTypeVariable(type);
+                    if (typeVariable != null) {
                         substitutedType = typeVariable.substitutionResult(replacement.getType());
                     }
                     else {