diff --git a/java/java.file.launcher/src/org/netbeans/modules/java/file/launcher/queries/MultiSourceRootProvider.java b/java/java.file.launcher/src/org/netbeans/modules/java/file/launcher/queries/MultiSourceRootProvider.java
index 7793d0663d79..0bfc6bfbc23d 100644
--- a/java/java.file.launcher/src/org/netbeans/modules/java/file/launcher/queries/MultiSourceRootProvider.java
+++ b/java/java.file.launcher/src/org/netbeans/modules/java/file/launcher/queries/MultiSourceRootProvider.java
@@ -94,8 +94,18 @@ public class MultiSourceRootProvider implements ClassPathProvider {
     private Map<FileObject, ClassPath> file2ClassPath = new WeakHashMap<>();
     private Map<FileObject, ClassPath> file2ModulePath = new WeakHashMap<>();
 
+    static boolean isSupportedFile(FileObject file) {
+        return SingleSourceFileUtil.isSingleSourceFile(file)
+                // MultiSourceRootProvider assumes it can convert FileObject to
+                // java.io.File, so filter here
+                && Objects.equals("file", file.toURI().getScheme());
+    }
+
     @Override
     public ClassPath findClassPath(FileObject file, String type) {
+        if (! isSupportedFile(file)) {
+            return null;
+        }
         switch (type) {
             case ClassPath.SOURCE: return getSourcePath(file);
             case ClassPath.COMPILE:
diff --git a/java/java.file.launcher/test/unit/src/org/netbeans/modules/java/file/launcher/SingleSourceFileUtilTest.java b/java/java.file.launcher/test/unit/src/org/netbeans/modules/java/file/launcher/SingleSourceFileUtilTest.java
index 5ad96c09c670..9bbd0d592ae7 100644
--- a/java/java.file.launcher/test/unit/src/org/netbeans/modules/java/file/launcher/SingleSourceFileUtilTest.java
+++ b/java/java.file.launcher/test/unit/src/org/netbeans/modules/java/file/launcher/SingleSourceFileUtilTest.java
@@ -82,4 +82,38 @@ public void testIsSupportedFile() throws IOException {
             }
         }
     }
+
+    @Test
+    public void testSsSingleSourceFile() throws IOException {
+        File vcsDemoDir = null;
+        File supportedFile = null;
+        File unsupportedFile = null;
+        File unsupportedFile2 = null;
+        try {
+            vcsDemoDir = Files.createTempDirectory("vcs-dummy").toFile();
+            supportedFile = Files.createTempFile("dummy", ".java").toFile();
+            unsupportedFile = new File(vcsDemoDir, "dummy.java");
+            unsupportedFile2 = Files.createTempFile("dummy", ".non-java").toFile();;
+            FileUtil.createData(unsupportedFile);
+
+            assertTrue(SingleSourceFileUtil.isSingleSourceFile(FileUtil.createData(supportedFile)));
+            assertFalse(SingleSourceFileUtil.isSingleSourceFile(FileUtil.createData(unsupportedFile)));
+            assertFalse(SingleSourceFileUtil.isSingleSourceFile(FileUtil.createData(unsupportedFile2)));
+
+        } finally {
+            if(supportedFile != null && supportedFile.exists()) {
+                supportedFile.delete();
+            }
+            if(unsupportedFile != null && unsupportedFile.exists()) {
+                unsupportedFile.delete();
+            }
+            if(unsupportedFile2 != null && unsupportedFile2.exists()) {
+                unsupportedFile2.delete();
+            }
+            if(vcsDemoDir != null && vcsDemoDir.exists()) {
+                vcsDemoDir.delete();
+            }
+        }
+    }
+
 }
diff --git a/java/java.file.launcher/test/unit/src/org/netbeans/modules/java/file/launcher/queries/MultiSourceRootProviderTest.java b/java/java.file.launcher/test/unit/src/org/netbeans/modules/java/file/launcher/queries/MultiSourceRootProviderTest.java
index 61694bb7845a..ff7245d3af48 100644
--- a/java/java.file.launcher/test/unit/src/org/netbeans/modules/java/file/launcher/queries/MultiSourceRootProviderTest.java
+++ b/java/java.file.launcher/test/unit/src/org/netbeans/modules/java/file/launcher/queries/MultiSourceRootProviderTest.java
@@ -18,7 +18,10 @@
  */
 package org.netbeans.modules.java.file.launcher.queries;
 
+import java.io.File;
+import java.io.IOException;
 import java.net.URI;
+import java.nio.file.Files;
 import java.util.Arrays;
 import java.util.HashSet;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -245,6 +248,22 @@ public void testBrokenOptions() throws Exception {
         provider.findClassPath(test, JavaClassPathConstants.MODULE_COMPILE_PATH);
     }
 
+    public void testMultiSourceRootProviderOnlySupportedForLocalFiles() throws IOException {
+        File supportedFile = null;
+        try {
+            supportedFile = Files.createTempFile("dummy", ".java").toFile();
+            FileObject realFileSource = FileUtil.createData(supportedFile);
+            FileObject inMemorySource = FileUtil.createMemoryFileSystem().getRoot().createData("Ahoj.java");
+
+            assertFalse(MultiSourceRootProvider.isSupportedFile(inMemorySource));
+            assertTrue(MultiSourceRootProvider.isSupportedFile(realFileSource));
+        } finally {
+            if(supportedFile != null && supportedFile.exists()) {
+                supportedFile.delete();
+            }
+        }
+    }
+
     @Override
     protected void setUp() throws Exception {
         super.setUp();