diff --git a/jps/jps-builders/src/org/jetbrains/jps/incremental/FSState.java b/jps/jps-builders/src/org/jetbrains/jps/incremental/FSState.java
index 066ec35812aa..a2ec11bd1ba7 100644
--- a/jps/jps-builders/src/org/jetbrains/jps/incremental/FSState.java
+++ b/jps/jps-builders/src/org/jetbrains/jps/incremental/FSState.java
@@ -24,7 +24,12 @@ public class FSState {
   private volatile FilesDelta myCurrentRoundDelta;
   private volatile FilesDelta myLastRoundDelta;
 
-  public FSState() {
+  // when true, will always determine dirty files by scanning FS and comparing timestamps
+  // alternatively, when false, after first scan will rely on extarnal notifications about changes
+  private final boolean myAlwaysScanFS;
+
+  public FSState(boolean alwaysScanFS) {
+    myAlwaysScanFS = alwaysScanFS;
   }
 
   public void onRebuild() {
@@ -35,6 +40,9 @@ public class FSState {
   }
 
   public boolean markInitialScanPerformed(Module module, boolean forTests) {
+    if (myAlwaysScanFS) {
+      return true;
+    }
     final Set<Module> map = forTests ? myInitialTestsScanPerformed : myInitialProductionScanPerformed;
     return map.add(module);
   }
diff --git a/jps/jps-builders/src/org/jetbrains/jps/server/ServerState.java b/jps/jps-builders/src/org/jetbrains/jps/server/ServerState.java
index 7e96b8ef018a..6fedae65e1a3 100644
--- a/jps/jps-builders/src/org/jetbrains/jps/server/ServerState.java
+++ b/jps/jps-builders/src/org/jetbrains/jps/server/ServerState.java
@@ -125,7 +125,7 @@ class ServerState {
       pd = myProjects.get(projectPath);
       if (pd == null) {
         final Project project = loadProject(projectPath, params);
-        final FSState fsState = new FSState();
+        final FSState fsState = new FSState(false);
         ProjectTimestamps timestamps = null;
         BuildDataManager dataManager = null;
         try {