diff --git a/engine/runtime/src/main/java/org/enso/interpreter/node/expression/builtin/interop/java/AddToClassPathNode.java b/engine/runtime/src/main/java/org/enso/interpreter/node/expression/builtin/interop/java/AddToClassPathNode.java
index 7442bde16576..551c3f8877d5 100644
--- a/engine/runtime/src/main/java/org/enso/interpreter/node/expression/builtin/interop/java/AddToClassPathNode.java
+++ b/engine/runtime/src/main/java/org/enso/interpreter/node/expression/builtin/interop/java/AddToClassPathNode.java
@@ -25,10 +25,9 @@ static AddToClassPathNode build() {
   @CompilerDirectives.TruffleBoundary
   @Specialization
   Object doExecute(Object path, @Cached ExpectStringNode expectStringNode) {
-    EnsoContext context = EnsoContext.get(this);
-    context
-        .getEnvironment()
-        .addToHostClassPath(context.getTruffleFile(new File(expectStringNode.execute(path))));
-    return context.getBuiltins().nothing();
+    var ctx = EnsoContext.get(this);
+    var file = ctx.getTruffleFile(new File(expectStringNode.execute(path)));
+    ctx.addToHostClassPath(file);
+    return ctx.getBuiltins().nothing();
   }
 }
diff --git a/engine/runtime/src/main/java/org/enso/interpreter/runtime/EnsoContext.java b/engine/runtime/src/main/java/org/enso/interpreter/runtime/EnsoContext.java
index 957c1ba7beb6..3c630f634de5 100644
--- a/engine/runtime/src/main/java/org/enso/interpreter/runtime/EnsoContext.java
+++ b/engine/runtime/src/main/java/org/enso/interpreter/runtime/EnsoContext.java
@@ -49,6 +49,7 @@
 import com.oracle.truffle.api.TruffleLanguage;
 import com.oracle.truffle.api.TruffleLanguage.Env;
 import com.oracle.truffle.api.TruffleLogger;
+import com.oracle.truffle.api.interop.InteropException;
 import com.oracle.truffle.api.interop.InteropLibrary;
 import com.oracle.truffle.api.interop.UnknownIdentifierException;
 import com.oracle.truffle.api.interop.UnsupportedMessageException;
@@ -383,6 +384,27 @@ public Optional<Module> findModuleByExpressionId(UUID expressionId) {
         .findFirst();
   }
 
+  /**
+   * Modifies the classpath to use to lookup {@code polyglot java} imports.
+   * @param file the file to register
+   */
+  @TruffleBoundary
+  public void addToHostClassPath(TruffleFile file) {
+    if (findGuestJava() == null) {
+      environment.addToHostClassPath(file);
+    } else {
+      try {
+        var path = new File(file.toUri()).getAbsoluteFile();
+        if (!path.exists()) {
+          throw new IllegalStateException("File not found " + path);
+        }
+        InteropLibrary.getUncached().invokeMember(findGuestJava(), "addPath", path.getPath());
+      } catch (InteropException ex) {
+        throw new IllegalStateException(ex);
+      }
+    }
+  }
+
   /**
    * Tries to lookup a Java class (host symbol in Truffle terminology) by its fully qualified name.
    * This method also tries to lookup inner classes. More specifically, if the provided name
@@ -401,24 +423,29 @@ public Object lookupJavaClass(String className) {
       List<String> nestedClassPart =
           i < items.size() - 1 ? items.subList(i + 1, items.size()) : List.of();
       try {
-        Object hostSymbol;
-        if (findGuestJava() == null) {
-          hostSymbol = environment.lookupHostSymbol(pkgName + "." + curClassName);
-        } else {
-          hostSymbol = InteropLibrary.getUncached().readMember(findGuestJava(), pkgName + "." + curClassName);
-        }
+        var hostSymbol = lookupHostSymbol(pkgName, curClassName);
         if (nestedClassPart.isEmpty()) {
           return hostSymbol;
         } else {
-          return getNestedClass(hostSymbol, nestedClassPart);
+          var fullInnerClassName = curClassName + "$" + String.join("$", nestedClassPart);
+          return lookupHostSymbol(pkgName, fullInnerClassName);
         }
-      } catch (RuntimeException | UnsupportedMessageException | UnknownIdentifierException ex) {
+      } catch (RuntimeException | InteropException ex) {
         logger.log(Level.WARNING, null, ex);
       }
     }
     return null;
   }
 
+  private Object lookupHostSymbol(String pkgName, String curClassName)
+  throws UnknownIdentifierException, UnsupportedMessageException {
+    if (findGuestJava() == null) {
+      return environment.lookupHostSymbol(pkgName + "." + curClassName);
+    } else {
+      return InteropLibrary.getUncached().readMember(findGuestJava(), pkgName + "." + curClassName);
+    }
+  }
+
   private Object guestJava = this;
 
   @TruffleBoundary
@@ -428,10 +455,14 @@ private Object findGuestJava() throws IllegalStateException {
     }
     guestJava = null;
     var envJava = System.getenv("ENSO_JAVA");
+    if (envJava == null) {
+      return guestJava;
+    }
     if ("espresso".equals(envJava)) {
       var src = Source.newBuilder("java", "<Bindings>", "getbindings.java").build();
       try {
         guestJava = environment.parsePublic(src).call();
+        logger.log(Level.SEVERE, "Using experimental Espresso support!");
       } catch (Exception ex) {
         if (ex.getMessage().contains("No language for id java found.")) {
           logger.log(Level.SEVERE, "Environment variable ENSO_JAVA=" + envJava + ", but " + ex.getMessage());
@@ -443,6 +474,8 @@ private Object findGuestJava() throws IllegalStateException {
           throw ise;
         }
       }
+    } else {
+      throw new IllegalStateException("Unsupported value of ENSO_JAVA environment variable: " + envJava);
     }
     return guestJava;
   }
@@ -641,30 +674,6 @@ public NotificationHandler getNotificationHandler() {
     return notificationHandler;
   }
 
-  private Object getNestedClass(Object hostClass, List<String> nestedClassName) {
-    Object nestedClass = hostClass;
-    var interop = InteropLibrary.getUncached();
-    for (String name : nestedClassName) {
-      if (interop.isMemberReadable(nestedClass, name)) {
-        Object member;
-        try {
-          member = interop.readMember(nestedClass, name);
-        } catch (UnsupportedMessageException | UnknownIdentifierException e) {
-          throw new IllegalStateException(e);
-        }
-        assert member != null;
-        if (interop.isMetaObject(member)) {
-          nestedClass = member;
-        } else {
-          return null;
-        }
-      } else {
-        return null;
-      }
-    }
-    return nestedClass;
-  }
-
   private <T> T getOption(OptionKey<T> key) {
     var options = getEnvironment().getOptions();
     var safely = false;
diff --git a/engine/runtime/src/main/scala/org/enso/interpreter/runtime/DefaultPackageRepository.scala b/engine/runtime/src/main/scala/org/enso/interpreter/runtime/DefaultPackageRepository.scala
index 413a8b9bd57e..9fceeb762e4c 100644
--- a/engine/runtime/src/main/scala/org/enso/interpreter/runtime/DefaultPackageRepository.scala
+++ b/engine/runtime/src/main/scala/org/enso/interpreter/runtime/DefaultPackageRepository.scala
@@ -181,7 +181,7 @@ private class DefaultPackageRepository(
     isLibrary: Boolean
   ): Unit = {
     val extensions = pkg.listPolyglotExtensions("java")
-    extensions.foreach(context.getEnvironment.addToHostClassPath)
+    extensions.foreach(context.addToHostClassPath)
 
     val (regularModules, syntheticModulesMetadata) = pkg
       .listSources()