diff --git a/platform/lang-impl/src/com/intellij/codeInsight/completion/CompletionProgressIndicator.java b/platform/lang-impl/src/com/intellij/codeInsight/completion/CompletionProgressIndicator.java
index 40be534520ef..056d4a99ae1b 100644
--- a/platform/lang-impl/src/com/intellij/codeInsight/completion/CompletionProgressIndicator.java
+++ b/platform/lang-impl/src/com/intellij/codeInsight/completion/CompletionProgressIndicator.java
@@ -571,6 +571,10 @@ public class CompletionProgressIndicator extends ProgressIndicatorBase implement
   }
 
   public void addWatchedPrefix(int startOffset, ElementPattern<String> restartCondition) {
+    int caret = myEditor.getCaretModel().getOffset();
+    if (caret < startOffset) {
+      LOG.error("caret=" + caret + "; start=" + startOffset);
+    }
     myRestartingPrefixConditions.add(Pair.create(startOffset, restartCondition));
   }
 
@@ -578,7 +582,11 @@ public class CompletionProgressIndicator extends ProgressIndicatorBase implement
     final CharSequence text = myEditor.getDocument().getCharsSequence();
     final int caretOffset = myEditor.getCaretModel().getOffset();
     for (Pair<Integer, ElementPattern<String>> pair : myRestartingPrefixConditions) {
-      final String newPrefix = text.subSequence(pair.first, caretOffset).toString();
+      int start = pair.first;
+      if (caretOffset < start) {
+        LOG.error("caret=" + caretOffset + "; start=" + start);
+      }
+      final String newPrefix = text.subSequence(start, caretOffset).toString();
       if (pair.second.accepts(newPrefix)) {
         scheduleRestart();
         myRestartingPrefixConditions.clear();