diff --git a/python/src/com/jetbrains/python/refactoring/PyRefactoringUtil.java b/python/src/com/jetbrains/python/refactoring/PyRefactoringUtil.java
index d392eb8adb91..44bda58e9990 100644
--- a/python/src/com/jetbrains/python/refactoring/PyRefactoringUtil.java
+++ b/python/src/com/jetbrains/python/refactoring/PyRefactoringUtil.java
@@ -75,10 +75,10 @@ public class PyRefactoringUtil {
     // Check if selection breaks AST node in binary expression
     if (parent instanceof PyBinaryExpression) {
       final String selection = file.getText().substring(element1.getTextOffset(), element2.getTextOffset() + element2.getTextLength());
-      final PyExpression expression =
-        PyElementGenerator.getInstance(project).createFromText(LanguageLevel.getDefault(), PyAssignmentStatement.class, "z=" + selection)
-          .getAssignedValue();
-      if (PsiUtilBase.hasErrorElementChild(expression)) {
+      final PyElementGenerator generator = PyElementGenerator.getInstance(project);
+      final LanguageLevel langLevel = LanguageLevel.forElement(element1);
+      final PyExpression expression = generator.createFromText(langLevel, PyAssignmentStatement.class, "z=" + selection).getAssignedValue();
+      if (PsiUtilBase.hasErrorElementChild(expression) || !(expression instanceof PyBinaryExpression)) {
         return null;
       }
       final String parentText = parent.getText();
@@ -91,13 +91,11 @@ public class PyRefactoringUtil {
       final String prefix = parentText.substring(0, startOffset);
       final String suffix = parentText.substring(endOffset, parentText.length());
       final TextRange textRange = TextRange.from(startOffset, endOffset - startOffset);
-      final PsiElement fakeExpression =
-        PyElementGenerator.getInstance(project).createFromText(LanguageLevel.getDefault(), parent.getClass(), prefix + "python" + suffix);
+      final PsiElement fakeExpression = generator.createFromText(langLevel, parent.getClass(), prefix + "python" + suffix);
       if (PsiUtilBase.hasErrorElementChild(fakeExpression)) {
         return null;
       }
 
-      assert expression != null;
       expression.putUserData(PyPsiUtils.SELECTION_BREAKS_AST_NODE, Pair.create(parent, textRange));
       return expression;
     }
diff --git a/python/testData/refactoring/introduceVariable/oneSidedSelection.py b/python/testData/refactoring/introduceVariable/oneSidedSelection.py
new file mode 100644
index 000000000000..a1c6d2b0a315
--- /dev/null
+++ b/python/testData/refactoring/introduceVariable/oneSidedSelection.py
@@ -0,0 +1 @@
+a = b <selection>+ func()</selection>
\ No newline at end of file
diff --git a/python/testSrc/com/jetbrains/python/refactoring/PyIntroduceVariableTest.java b/python/testSrc/com/jetbrains/python/refactoring/PyIntroduceVariableTest.java
index c866b98a6cfb..d73eab1ab2ac 100644
--- a/python/testSrc/com/jetbrains/python/refactoring/PyIntroduceVariableTest.java
+++ b/python/testSrc/com/jetbrains/python/refactoring/PyIntroduceVariableTest.java
@@ -45,6 +45,14 @@ public class PyIntroduceVariableTest extends PyIntroduceTestCase {
   }
   
   public void testIncorrectSelection() {  // PY-4455
+    doTestCannotPerform();
+  }
+  
+  public void testOneSidedSelection() {  // PY-4456
+    doTestCannotPerform();
+  }
+
+  private void doTestCannotPerform() {
     boolean thrownExpectedException = false;
     try {
       doTest();