diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/NamespaceCodegen.java b/compiler/backend/src/org/jetbrains/jet/codegen/NamespaceCodegen.java
index 6349b106159..9063e470cba 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/NamespaceCodegen.java
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/NamespaceCodegen.java
@@ -35,6 +35,7 @@ import org.jetbrains.jet.lang.resolve.name.FqName;
 import org.jetbrains.jet.lang.resolve.name.Name;
 import org.jetbrains.jet.utils.Progress;
 
+import java.io.File;
 import java.util.Collection;
 
 import static org.jetbrains.asm4.Opcodes.*;
@@ -151,9 +152,8 @@ public class NamespaceCodegen {
 
             if (k > 0) {
                 PsiFile containingFile = file.getContainingFile();
-                String fname = containingFile.getName();
-                fname = fname.substring(0, fname.lastIndexOf('.'));
-                String className = name.child(Name.identifier("namespace$src$" + fname)).getFqName().replace('.', '/');
+                String namespaceInternalName = name.child(Name.identifier(JvmAbi.PACKAGE_CLASS)).getFqName().replace('.', '/');
+                String className = getMultiFileNamespaceInternalName(namespaceInternalName, containingFile);
                 ClassBuilder builder = state.forNamespacepart(className);
 
                 builder.defineClass(containingFile, V1_6,
@@ -282,4 +282,18 @@ public class NamespaceCodegen {
 
         return JvmClassName.byInternalName(fqName.getFqName().replace('.', '/') + "/" + JvmAbi.PACKAGE_CLASS);
     }
+
+    @NotNull
+    public static String getMultiFileNamespaceInternalName(String namespaceInternalName, PsiFile file) {
+        String name = file.getName();
+
+        int substringFrom = name.lastIndexOf(File.separator) + 1;
+
+        int substringTo = name.lastIndexOf('.');
+        if (substringTo == -1) {
+            substringTo = name.length();
+        }
+
+        return namespaceInternalName + "$src$" + name.substring(substringFrom, substringTo);
+    }
 }
diff --git a/idea/src/org/jetbrains/jet/plugin/debugger/JetPositionManager.java b/idea/src/org/jetbrains/jet/plugin/debugger/JetPositionManager.java
index f949a84c18a..565c78aeaf8 100644
--- a/idea/src/org/jetbrains/jet/plugin/debugger/JetPositionManager.java
+++ b/idea/src/org/jetbrains/jet/plugin/debugger/JetPositionManager.java
@@ -159,8 +159,7 @@ public class JetPositionManager implements PositionManager {
                     boolean multiFileNamespace = typeMapper.getClosureAnnotator().isMultiFileNamespace(fqName);
                     String namespaceInternalName = NamespaceCodegen.getJVMClassNameForKotlinNs(fqName).getInternalName();
                     if (multiFileNamespace) {
-                        String name = namespace.getName();
-                        result.set(namespaceInternalName + "$src$" + name.substring(0, name.lastIndexOf('.')));
+                        result.set(NamespaceCodegen.getMultiFileNamespaceInternalName(namespaceInternalName, namespace));
                     }
                     else {
                         result.set(namespaceInternalName);