diff --git a/platform/core-api/src/com/intellij/util/indexing/ID.java b/platform/core-api/src/com/intellij/util/indexing/ID.java
index a901214fb83d..4837e0a0d634 100644
--- a/platform/core-api/src/com/intellij/util/indexing/ID.java
+++ b/platform/core-api/src/com/intellij/util/indexing/ID.java
@@ -43,23 +43,37 @@ public class ID<K, V> {
     final File indices = getEnumFile();
     try {
       final BufferedReader reader = new BufferedReader(new FileReader(indices));
+      TObjectIntHashMap<String> nameToIdRegistry = new TObjectIntHashMap<String>();
       try {
         int cnt = 0;
         do {
             cnt++;
             final String name = reader.readLine();
             if (name == null) break;
-            ourNameToIdRegistry.put(name, cnt);
+            nameToIdRegistry.put(name, cnt);
           }
           while (true);
       }
       finally {
         reader.close();
       }
+
+      synchronized (ourNameToIdRegistry) {
+        ourNameToIdRegistry.ensureCapacity(nameToIdRegistry.size());
+        nameToIdRegistry.forEachEntry(new TObjectIntProcedure<String>() {
+          @Override
+          public boolean execute(String name, int index) {
+            ourNameToIdRegistry.put(name, index);
+            return true;
+          }
+        });
+      }
     }
     catch (IOException e) {
-      ourNameToIdRegistry.clear();
-      writeEnumFile();
+      synchronized (ourNameToIdRegistry) {
+        ourNameToIdRegistry.clear();
+        writeEnumFile();
+      }
     }
   }
 
@@ -77,18 +91,18 @@ public class ID<K, V> {
   }
 
   private static short stringToId(String name) {
-    if (ourNameToIdRegistry.containsKey(name)) {
-      return (short)ourNameToIdRegistry.get(name);
+    synchronized (ourNameToIdRegistry) {
+      if (ourNameToIdRegistry.containsKey(name)) {
+        return (short)ourNameToIdRegistry.get(name);
+      }
+
+      int n = ourNameToIdRegistry.size() + 1;
+      assert n <= MAX_NUMBER_OF_INDICES : "Number of indices exceeded";
+
+      ourNameToIdRegistry.put(name, n);
+      writeEnumFile();
+      return (short)n;
     }
-
-    int n = ourNameToIdRegistry.size() + 1;
-    assert n <= MAX_NUMBER_OF_INDICES : "Number of indices exceeded";
-
-    ourNameToIdRegistry.put(name, n);
-
-    writeEnumFile();
-
-    return (short)n;
   }
 
   private static void writeEnumFile() {