diff --git a/python/src/com/jetbrains/python/validation/CompatibilityVisitor.java b/python/src/com/jetbrains/python/validation/CompatibilityVisitor.java
index 67a7306a61b2..4e60035be074 100644
--- a/python/src/com/jetbrains/python/validation/CompatibilityVisitor.java
+++ b/python/src/com/jetbrains/python/validation/CompatibilityVisitor.java
@@ -50,10 +50,10 @@ public abstract class CompatibilityVisitor extends PyAnnotator {
     AVAILABLE_PREFIXES.put(LanguageLevel.PYTHON30, Sets.newHashSet("R", "B"));
     AVAILABLE_PREFIXES.put(LanguageLevel.PYTHON31, Sets.newHashSet("R", "B", "BR"));
     AVAILABLE_PREFIXES.put(LanguageLevel.PYTHON32, Sets.newHashSet("R", "B", "BR"));
-    AVAILABLE_PREFIXES.put(LanguageLevel.PYTHON33, Sets.newHashSet("R", "U", "B", "BR", "RB"));
-    AVAILABLE_PREFIXES.put(LanguageLevel.PYTHON34, Sets.newHashSet("R", "U", "B", "BR", "RB"));
   }
 
+  private static final Set<String> DEFAULT_PREFIXES = Sets.newHashSet(Sets.newHashSet("R", "U", "B", "BR", "RB"));
+
   public CompatibilityVisitor(List<LanguageLevel> versionsToProcess) {
     myVersionsToProcess = versionsToProcess;
   }
@@ -254,7 +254,8 @@ public abstract class CompatibilityVisitor extends PyAnnotator {
         final LanguageLevel languageLevel = myVersionsToProcess.get(i);
         if (prefix.isEmpty()) continue;
 
-        final Set<String> prefixes = AVAILABLE_PREFIXES.get(languageLevel);
+        final Set<String> prefixesForLanguageLevel = AVAILABLE_PREFIXES.get(languageLevel);
+        final Set<String> prefixes = prefixesForLanguageLevel != null ? prefixesForLanguageLevel : DEFAULT_PREFIXES;
         if (!prefixes.contains(prefix))
           len = appendLanguageLevel(message, len, languageLevel);
       }