diff --git a/src/main/c/src/EndpointDescriptor.c b/src/main/c/src/EndpointDescriptor.c
index 109795a..24c79c7 100644
--- a/src/main/c/src/EndpointDescriptor.c
+++ b/src/main/c/src/EndpointDescriptor.c
@@ -39,7 +39,10 @@ JNIEXPORT jbyte JNICALL METHOD_NAME(EndpointDescriptor, bLength)
     JNIEnv *env, jobject this
 )
 {
-    return unwrapEndpointDescriptor(env, this)->bLength;
+    struct libusb_endpoint_descriptor* descriptor =
+        unwrapEndpointDescriptor(env, this);
+    if (!descriptor) return 0;
+    return descriptor->bLength;
 }
 
 /**
@@ -50,7 +53,10 @@ JNIEXPORT jbyte JNICALL METHOD_NAME(EndpointDescriptor, bDescriptorType)
     JNIEnv *env, jobject this
 )
 {
-    return unwrapEndpointDescriptor(env, this)->bDescriptorType;
+    struct libusb_endpoint_descriptor* descriptor =
+        unwrapEndpointDescriptor(env, this);
+    if (!descriptor) return 0;
+    return descriptor->bDescriptorType;
 }
 
 /**
@@ -61,7 +67,10 @@ JNIEXPORT jbyte JNICALL METHOD_NAME(EndpointDescriptor, bEndpointAddress)
     JNIEnv *env, jobject this
 )
 {
-    return unwrapEndpointDescriptor(env, this)->bEndpointAddress;
+    struct libusb_endpoint_descriptor* descriptor =
+        unwrapEndpointDescriptor(env, this);
+    if (!descriptor) return 0;
+    return descriptor->bEndpointAddress;
 }
 
 /**
@@ -72,7 +81,10 @@ JNIEXPORT jbyte JNICALL METHOD_NAME(EndpointDescriptor, bmAttributes)
     JNIEnv *env, jobject this
 )
 {
-    return unwrapEndpointDescriptor(env, this)->bmAttributes;
+    struct libusb_endpoint_descriptor* descriptor =
+        unwrapEndpointDescriptor(env, this);
+    if (!descriptor) return 0;
+    return descriptor->bmAttributes;
 }
 
 /**
@@ -83,7 +95,10 @@ JNIEXPORT jshort JNICALL METHOD_NAME(EndpointDescriptor, wMaxPacketSize)
     JNIEnv *env, jobject this
 )
 {
-    return unwrapEndpointDescriptor(env, this)->wMaxPacketSize;
+    struct libusb_endpoint_descriptor* descriptor =
+        unwrapEndpointDescriptor(env, this);
+    if (!descriptor) return 0;
+    return descriptor->wMaxPacketSize;
 }
 
 /**
@@ -94,7 +109,10 @@ JNIEXPORT jbyte JNICALL METHOD_NAME(EndpointDescriptor, bInterval)
     JNIEnv *env, jobject this
 )
 {
-    return unwrapEndpointDescriptor(env, this)->bInterval;
+    struct libusb_endpoint_descriptor* descriptor =
+        unwrapEndpointDescriptor(env, this);
+    if (!descriptor) return 0;
+    return descriptor->bInterval;
 }
 
 /**
@@ -105,7 +123,10 @@ JNIEXPORT jbyte JNICALL METHOD_NAME(EndpointDescriptor, bRefresh)
     JNIEnv *env, jobject this
 )
 {
-    return unwrapEndpointDescriptor(env, this)->bRefresh;
+    struct libusb_endpoint_descriptor* descriptor =
+        unwrapEndpointDescriptor(env, this);
+    if (!descriptor) return 0;
+    return descriptor->bRefresh;
 }
 
 /**
@@ -116,7 +137,10 @@ JNIEXPORT jint JNICALL METHOD_NAME(EndpointDescriptor, bSynchAddress)
     JNIEnv *env, jobject this
 )
 {
-    return unwrapEndpointDescriptor(env, this)->bSynchAddress;
+    struct libusb_endpoint_descriptor* descriptor =
+        unwrapEndpointDescriptor(env, this);
+    if (!descriptor) return 0;
+    return descriptor->bSynchAddress;
 }
 
 /**
@@ -129,6 +153,7 @@ JNIEXPORT jobject JNICALL METHOD_NAME(EndpointDescriptor, extra)
 {
     struct libusb_endpoint_descriptor *descriptor =
         unwrapEndpointDescriptor(env, this);
+    if (!descriptor) return NULL;
     return (*env)->NewDirectByteBuffer(env, (void *) descriptor->extra,
         descriptor->extra_length);
 }
@@ -141,5 +166,8 @@ JNIEXPORT jint JNICALL METHOD_NAME(EndpointDescriptor, extraLength)
     JNIEnv *env, jobject this
 )
 {
-    return unwrapEndpointDescriptor(env, this)->extra_length;
+    struct libusb_endpoint_descriptor* descriptor =
+        unwrapEndpointDescriptor(env, this);
+    if (!descriptor) return 0;
+    return descriptor->extra_length;
 }
diff --git a/src/test/java/de/ailis/usb4java/libusb/EndpointDescriptorTest.java b/src/test/java/de/ailis/usb4java/libusb/EndpointDescriptorTest.java
new file mode 100644
index 0000000..f828754
--- /dev/null
+++ b/src/test/java/de/ailis/usb4java/libusb/EndpointDescriptorTest.java
@@ -0,0 +1,153 @@
+/*
+ * Copyright (C) 2013 Klaus Reimer <k@ailis.de>
+ * See LICENSE.md for licensing information.
+ */
+
+package de.ailis.usb4java.libusb;
+
+import static de.ailis.usb4java.test.UsbAssume.assumeUsbTestsEnabled;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Tests the {@link EndpointDescriptor} class.
+ * 
+ * @author Klaus Reimer (k@ailis.de)
+ */
+public class EndpointDescriptorTest
+{
+    /** The test subject. */
+    private EndpointDescriptor descriptor;
+
+    /**
+     * Setup test.
+     */
+    @Before
+    public void setUp()
+    {
+        assumeUsbTestsEnabled();
+        LibUsb.init(null);
+        this.descriptor = new EndpointDescriptor();
+    }
+    
+    /**
+     * Tear down test.
+     */
+    @After    
+    public void tearDown()
+    {
+        LibUsb.exit(null);
+    }
+
+    /**
+     * Tests uninitialized access to
+     * {@link EndpointDescriptor#bLength()}
+     */
+    @Test(expected = IllegalStateException.class)
+    public void testUninitializedLength()
+    {
+        assumeUsbTestsEnabled();
+        this.descriptor.bLength();
+    }
+
+    /**
+     * Tests uninitialized access to
+     * {@link EndpointDescriptor#bDescriptorType()}
+     */
+    @Test(expected = IllegalStateException.class)
+    public void testUninitializedDescriptorType()
+    {
+        assumeUsbTestsEnabled();
+        this.descriptor.bDescriptorType();
+    }
+    
+    /**
+     * Tests uninitialized access to
+     * {@link EndpointDescriptor#bEndpointAddress()}
+     */
+    @Test(expected = IllegalStateException.class)
+    public void testUninitializedEndpointAddress()
+    {
+        assumeUsbTestsEnabled();
+        this.descriptor.bEndpointAddress();
+    }
+    
+    /**
+     * Tests uninitialized access to
+     * {@link EndpointDescriptor#bmAttributes()}
+     */
+    @Test(expected = IllegalStateException.class)
+    public void testUninitializedAttributes()
+    {
+        assumeUsbTestsEnabled();
+        this.descriptor.bmAttributes();
+    }
+
+    /**
+     * Tests uninitialized access to
+     * {@link EndpointDescriptor#wMaxPacketSize()}
+     */
+    @Test(expected = IllegalStateException.class)
+    public void testUninitializedMaxPacketSize()
+    {
+        assumeUsbTestsEnabled();
+        this.descriptor.wMaxPacketSize();
+    }
+
+    /**
+     * Tests uninitialized access to
+     * {@link EndpointDescriptor#bInterval()}
+     */
+    @Test(expected = IllegalStateException.class)
+    public void testUninitializedInterval()
+    {
+        assumeUsbTestsEnabled();
+        this.descriptor.bInterval();
+    }
+    
+    /**
+     * Tests uninitialized access to
+     * {@link EndpointDescriptor#bRefresh()}
+     */
+    @Test(expected = IllegalStateException.class)
+    public void testUninitializedRefresh()
+    {
+        assumeUsbTestsEnabled();
+        this.descriptor.bRefresh();
+    }
+    
+    /**
+     * Tests uninitialized access to
+     * {@link EndpointDescriptor#bSynchAddress()}
+     */
+    @Test(expected = IllegalStateException.class)
+    public void testUninitializedSynchAddress()
+    {
+        assumeUsbTestsEnabled();
+        this.descriptor.bSynchAddress();
+    }
+    
+    /**
+     * Tests uninitialized access to
+     * {@link EndpointDescriptor#extra()}
+     */
+    @Test(expected = IllegalStateException.class)
+    public void testUninitializedExtra()
+    {
+        assumeUsbTestsEnabled();
+        this.descriptor.extra();
+    }
+
+    /**
+     * Tests uninitialized access to
+     * {@link EndpointDescriptor#extraLength()}
+     */
+    @Test(expected = IllegalStateException.class)
+    public void testUninitializedExtraLength()
+    {
+        assumeUsbTestsEnabled();
+        this.descriptor.extraLength();
+    }
+}