diff --git a/plugins/spellchecker/src/com/intellij/spellchecker/compress/Encoder.java b/plugins/spellchecker/src/com/intellij/spellchecker/compress/Encoder.java
index 5aba9c2fd77d..d28f4d399dd0 100644
--- a/plugins/spellchecker/src/com/intellij/spellchecker/compress/Encoder.java
+++ b/plugins/spellchecker/src/com/intellij/spellchecker/compress/Encoder.java
@@ -25,7 +25,7 @@ public final class Encoder {
 
   @Nullable
   public UnitBitSet encode(@NotNull CharSequence letters, boolean force) throws EncodingException {
-    if (UnitBitSet.MAX_CHARS_IN_WORD <= letters.length()) return null;
+    if (UnitBitSet.MAX_CHARS_IN_WORD <= letters.length() + offset) return null;
     int unknownLetters = 0;
     UnitBitSet bs = new UnitBitSet();
     for (int i = 0; i < letters.length(); i++) {