diff --git a/com.google.eclipse.protobuf.ui/META-INF/MANIFEST.MF b/com.google.eclipse.protobuf.ui/META-INF/MANIFEST.MF
index ad89cad..87abba7 100644
--- a/com.google.eclipse.protobuf.ui/META-INF/MANIFEST.MF
+++ b/com.google.eclipse.protobuf.ui/META-INF/MANIFEST.MF
@@ -16,7 +16,8 @@
  org.eclipse.core.runtime,
  com.ibm.icu,
  org.eclipse.emf.databinding,
- org.eclipse.core.resources
+ org.eclipse.core.resources,
+ org.eclipse.core.filesystem;bundle-version="1.3.100"
 Import-Package: org.apache.log4j,
  org.apache.commons.logging
 Bundle-RequiredExecutionEnvironment: J2SE-1.5
diff --git a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/scoping/FileResolverStrategy.java b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/scoping/FileResolverStrategy.java
index 15c6e5d..7f46b50 100644
--- a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/scoping/FileResolverStrategy.java
+++ b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/scoping/FileResolverStrategy.java
@@ -8,6 +8,7 @@
  */
 package com.google.eclipse.protobuf.ui.scoping;
 
+import org.eclipse.core.runtime.IPath;
 import org.eclipse.emf.common.util.URI;
 
 import com.google.eclipse.protobuf.ui.preferences.paths.PathsPreferences;
@@ -18,7 +19,7 @@
 interface FileResolverStrategy {
 
   String PREFIX = "platform:/resource";
-  String SEPARATOR = "/";
+  char SEPARATOR = IPath.SEPARATOR;
 
   String resolveUri(String importUri, URI declaringResourceUri, PathsPreferences preferences);
 }
diff --git a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/scoping/MultipleDirectoriesFileResolver.java b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/scoping/MultipleDirectoriesFileResolver.java
index abb6877..6379c7d 100644
--- a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/scoping/MultipleDirectoriesFileResolver.java
+++ b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/scoping/MultipleDirectoriesFileResolver.java
@@ -8,6 +8,9 @@
  */
 package com.google.eclipse.protobuf.ui.scoping;
 
+import org.eclipse.core.filesystem.*;
+import org.eclipse.core.runtime.IPath;
+import org.eclipse.core.runtime.Path;
 import org.eclipse.emf.common.util.URI;
 
 import com.google.eclipse.protobuf.ui.preferences.paths.DirectoryPath;
@@ -27,16 +30,28 @@
   /** {@inheritDoc} */
   public String resolveUri(String importUri, URI declaringResourceUri, PathsPreferences preferences) {
     for (DirectoryPath directoryPath : preferences.directoryPaths()) {
-      if (!directoryPath.isWorkspacePath()) continue; // TODO file system is not supported yet.
-      String resolved = resolveUriInWorkspace(importUri, directoryPath.value());
+      String resolved = resolveUri(importUri, directoryPath);
       if (resolved != null) return resolved;
     }
     return null;
   }
 
-  private String resolveUriInWorkspace(String importUri, String directoryName) {
-    String path = PREFIX + directoryName + SEPARATOR + importUri;
+  private String resolveUri(String importUri, DirectoryPath directoryPath) {
+    if (directoryPath.isWorkspacePath()) return resolveUriInWorkspace(importUri, directoryPath.value());
+    return resolveUriFileSystem(importUri, directoryPath.value());
+  }
+
+  private String resolveUriInWorkspace(String importUri, String directoryPath) {
+    String path = PREFIX + directoryPath + SEPARATOR + importUri;
     boolean exists = resources.fileExists(URI.createURI(path));
     return (exists) ? path : null;
   }
+
+  private String resolveUriFileSystem(String importUri, String directoryPath) {
+    IFileSystem fileSystem = EFS.getLocalFileSystem();
+    IPath path = new Path(directoryPath + SEPARATOR + importUri);
+    IFileInfo fileInfo = fileSystem.getStore(path).fetchInfo();
+    if (!fileInfo.exists()) return null;
+    return URIUtil.toURI(path).toString();
+  }
 }