diff --git a/src/main/c/src/LibUsb.c b/src/main/c/src/LibUsb.c
index 99e22ef..748cf64 100644
--- a/src/main/c/src/LibUsb.c
+++ b/src/main/c/src/LibUsb.c
@@ -23,6 +23,8 @@
 #include "ConfigDescriptor.h"
 #include "Transfer.h"
 
+static int defaultContextRefcnt = 0;
+
 /**
  * Version getVersion()
  */
@@ -44,7 +46,9 @@ JNIEXPORT jint JNICALL METHOD_NAME(LibUsb, init)
 {
     if (!context)
     {
-        return libusb_init(NULL);
+        int result = libusb_init(NULL);
+        if (result == LIBUSB_SUCCESS) defaultContextRefcnt++;
+        return result;
     }
     else
     {
@@ -65,19 +69,23 @@ JNIEXPORT void JNICALL METHOD_NAME(LibUsb, exit)
     JNIEnv *env, jclass class, jobject context
 )
 {
-	if (!context)
-	{
-		libusb_exit(NULL);
-	}
-	else
-	{
-		libusb_context *ctx = unwrapContext(env, context);
-		if (!ctx) return;
+    if (!context)
+    {
+        if (defaultContextRefcnt <= 0) return;
+
+        libusb_exit(NULL);
+
+        defaultContextRefcnt--;
+    }
+    else
+    {
+        libusb_context *ctx = unwrapContext(env, context);
+        if (!ctx) return;
 
         libusb_exit(ctx);
 
         resetContext(env, context);
-	}
+    }
 }
 
 /**
diff --git a/src/main/java/de/ailis/usb4java/libusb/LibUsb.java b/src/main/java/de/ailis/usb4java/libusb/LibUsb.java
index a48f0a3..cceac40 100644
--- a/src/main/java/de/ailis/usb4java/libusb/LibUsb.java
+++ b/src/main/java/de/ailis/usb4java/libusb/LibUsb.java
@@ -525,7 +525,7 @@ public final class LibUsb
      * 
      * @see <a href="http://libusbx.sf.net/api-1.0/contexts.html">Contexts</a>
      */
-    public static native int init(final Context context);
+    public static synchronized native int init(final Context context);
 
     /**
      * Deinitialize libusb.
@@ -537,7 +537,7 @@ public final class LibUsb
      *            The {@link Context} to deinitialize, or NULL for the default
      *            context.
      */
-    public static native void exit(final Context context);
+    public static synchronized native void exit(final Context context);
 
     /**
      * Set log message verbosity.