diff --git a/python/src/com/jetbrains/python/codeInsight/stdlib/PyStdlibCanonicalPathProvider.java b/python/src/com/jetbrains/python/codeInsight/stdlib/PyStdlibCanonicalPathProvider.java
index 7ea5d66d6498..55bf2713fe84 100644
--- a/python/src/com/jetbrains/python/codeInsight/stdlib/PyStdlibCanonicalPathProvider.java
+++ b/python/src/com/jetbrains/python/codeInsight/stdlib/PyStdlibCanonicalPathProvider.java
@@ -36,7 +36,7 @@ public class PyStdlibCanonicalPathProvider implements PyCanonicalPathProvider {
 
   public static QualifiedName restoreStdlibCanonicalPath(QualifiedName qName) {
     if (qName.getComponentCount() > 0) {
-      final List<String> components = qName.getComponents();
+      final List<String> components = new ArrayList<>(qName.getComponents());
       final String head = components.get(0);
       if (head.equals("_abcoll") || head.equals("_collections") || head.equals("_collections_abc")) {
         components.set(0, "collections");
diff --git a/python/src/com/jetbrains/python/psi/resolve/PythonPathCache.java b/python/src/com/jetbrains/python/psi/resolve/PythonPathCache.java
index fe55f0b65aa5..e6ac00179580 100644
--- a/python/src/com/jetbrains/python/psi/resolve/PythonPathCache.java
+++ b/python/src/com/jetbrains/python/psi/resolve/PythonPathCache.java
@@ -24,6 +24,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -53,7 +54,7 @@ public abstract class PythonPathCache {
       // At least one element is invalid
       return null;
     }
-    return elements;
+    return elements != null ? Collections.unmodifiableList(elements) : null;
   }
 
   public void put(QualifiedName qualifiedName, List<PsiElement> results) {
@@ -67,7 +68,8 @@ public abstract class PythonPathCache {
     if (vFile == null) {
       return null;
     }
-    return myQNameCache.get(vFile.getUrl());
+    final List<QualifiedName> names = myQNameCache.get(vFile.getUrl());
+    return names != null ? Collections.unmodifiableList(names) : null;
   }
 
   public void putNames(VirtualFile vFile, List<QualifiedName> qNames) {