diff --git a/src/java/org/lwjgl/Sys.java b/src/java/org/lwjgl/Sys.java
index 7d446484..91f2468c 100644
--- a/src/java/org/lwjgl/Sys.java
+++ b/src/java/org/lwjgl/Sys.java
@@ -47,6 +47,8 @@ import org.lwjgl.input.Mouse;
  * @version $Revision$
  */
 public final class Sys {
+	public static final String VERSION = "0.9pre";
+
 	/** Low process priority. @see #setProcessPriority() */
 	public static final int LOW_PRIORITY = -1;
 
@@ -78,9 +80,9 @@ public final class Sys {
 
 	/** The native library name */
 	private static String LIBRARY_NAME = "lwjgl";
-  
-  /** The platform being executed on */
-  private static String PLATFORM;
+
+	/** The platform being executed on */
+	private static String PLATFORM;
 	
 	/**
 	 * Debug flag.
@@ -91,12 +93,6 @@ public final class Sys {
 
 	static {
 		initialize();
-
-    // check platform name, and default to awt
-    PLATFORM = System.getProperty("org.lwjgl.Sys.platform");
-    if(PLATFORM == null) {
-      PLATFORM = "org.lwjgl.SwingAdapter";
-    }
 	}
 
 	/**
@@ -130,9 +126,19 @@ public final class Sys {
 			return;
 		initialized = true;
 		System.loadLibrary(LIBRARY_NAME);
+		String native_version = getNativeLibraryVersion();
+		if (!native_version.equals(VERSION))
+			throw new IllegalStateException("Version mismatch: jar version is '" + VERSION + 
+                                                        "', native libary version is '" + native_version + "'");
 		setDebug(DEBUG);
 		setTime(0);
 
+		// check platform name, and default to awt
+		PLATFORM = System.getProperty("org.lwjgl.Sys.platform");
+		if(PLATFORM == null) {
+			PLATFORM = "org.lwjgl.SwingAdapter";
+		}
+
 		Runtime.getRuntime().addShutdownHook(new Thread() {
 			public void run() {
 				Display.resetDisplayMode();
@@ -148,7 +154,12 @@ public final class Sys {
 	}
 
 	/**
-     * Set the debug level of the native library
+	 * Return the version of the native library
+	 */
+	private static native String getNativeLibraryVersion();
+
+	/**
+	 * Set the debug level of the native library
 	 */
 	private static native void setDebug(boolean debug);
 
diff --git a/src/native/common/checkALerror.h b/src/native/common/checkALerror.h
index 1cacc2b9..3c02e894 100644
--- a/src/native/common/checkALerror.h
+++ b/src/native/common/checkALerror.h
@@ -16,7 +16,7 @@
 
 #define CHECK_AL_ERROR \
 	{ \
-		if (ISDEBUGENABLED()) { \
+		if (isDebugEnabled()) { \
 			int err = alGetError(); \
 			if (err != AL_NO_ERROR) { \
 				jclass cls = env->FindClass("org/lwjgl/openal/OpenALException"); \
@@ -28,7 +28,7 @@
 /* only available if deviceaddress is specified in method */
 #define CHECK_ALC_ERROR \
 	{ \
-		if (ISDEBUGENABLED()) { \
+		if (isDebugEnabled()) { \
 			int err = alcGetError((ALCdevice*) deviceaddress); \
 			if (err != AL_NO_ERROR) { \
 				jclass cls = env->FindClass("org/lwjgl/openal/OpenALException"); \
diff --git a/src/native/common/common_tools.cpp b/src/native/common/common_tools.cpp
index 794dd4d7..8b77f6a6 100644
--- a/src/native/common/common_tools.cpp
+++ b/src/native/common/common_tools.cpp
@@ -40,7 +40,16 @@
 #include <stdlib.h>
 #include "common_tools.h"
 
-bool debug = false;
+static bool debug = false;
+static const char* VERSION = "0.9pre";
+
+jstring getVersionString(JNIEnv *env) {
+	return env->NewStringUTF(VERSION);
+}
+
+bool isDebugEnabled(void) {
+	return debug;
+}
 
 void setDebugEnabled(bool enable) {
 	debug = enable;
@@ -49,7 +58,7 @@ void setDebugEnabled(bool enable) {
 void printfDebug(const char *format, ...) {
 	va_list ap;
 	va_start(ap, format);
-	if (ISDEBUGENABLED())
+	if (isDebugEnabled())
 		vfprintf(stderr, format, ap);
 	va_end(ap);
 }
diff --git a/src/native/common/common_tools.h b/src/native/common/common_tools.h
index 5b103cad..0c04e537 100644
--- a/src/native/common/common_tools.h
+++ b/src/native/common/common_tools.h
@@ -43,11 +43,8 @@
 #include <jni.h>
 #include "org_lwjgl_Sys.h"
 
-extern bool debug;
-
 // Must be x * max_event_size + 1
 #define EVENT_BUFFER_SIZE (25 * 4 + 1)
-#define ISDEBUGENABLED() (debug)
 
 typedef struct {
 	unsigned char input_event_buffer[EVENT_BUFFER_SIZE];
@@ -56,6 +53,8 @@ typedef struct {
 	int list_end;
 } event_queue_t;
 
+extern bool isDebugEnabled(void);
+extern jstring getVersionString(JNIEnv *env);
 extern void initEventQueue(event_queue_t *event_queue);
 extern int copyEvents(event_queue_t *event_queue, unsigned char *output_event_buffer, int buffer_size, int event_size);
 extern void putEventElement(event_queue_t *queue, unsigned char byte);
diff --git a/src/native/common/org_lwjgl_Sys.h b/src/native/common/org_lwjgl_Sys.h
index e7e5020a..f1830088 100644
--- a/src/native/common/org_lwjgl_Sys.h
+++ b/src/native/common/org_lwjgl_Sys.h
@@ -16,7 +16,17 @@ extern "C" {
 #undef org_lwjgl_Sys_REALTIME_PRIORITY
 #define org_lwjgl_Sys_REALTIME_PRIORITY 2L
 /* Inaccessible static: LIBRARY_NAME */
+/* Inaccessible static: PLATFORM */
 /* Inaccessible static: DEBUG */
+/* Inaccessible static: initialized */
+/*
+ * Class:     org_lwjgl_Sys
+ * Method:    getNativeLibraryVersion
+ * Signature: ()Ljava/lang/String;
+ */
+JNIEXPORT jstring JNICALL Java_org_lwjgl_Sys_getNativeLibraryVersion
+  (JNIEnv *, jclass);
+
 /*
  * Class:     org_lwjgl_Sys
  * Method:    setDebug
diff --git a/src/native/linux/org_lwjgl_Sys.cpp b/src/native/linux/org_lwjgl_Sys.cpp
index 9f568dd3..1557d545 100644
--- a/src/native/linux/org_lwjgl_Sys.cpp
+++ b/src/native/linux/org_lwjgl_Sys.cpp
@@ -165,6 +165,10 @@ JNIEXPORT void JNICALL Java_org_lwjgl_Sys_nAlert(JNIEnv * env, jclass clazz, jst
 	env->ReleaseStringUTFChars(title, cTitleBarText);
 }
 
+JNIEXPORT jstring JNICALL Java_org_lwjgl_Sys_getNativeLibraryVersion(JNIEnv *env, jclass clazz) {
+	return getVersionString(env);
+}
+
 /*
  * Class:     org_lwjgl_Sys
  * Method:    openURL
diff --git a/src/native/linux/org_lwjgl_opengl_Window.cpp b/src/native/linux/org_lwjgl_opengl_Window.cpp
index f6c348a8..91e09d7c 100644
--- a/src/native/linux/org_lwjgl_opengl_Window.cpp
+++ b/src/native/linux/org_lwjgl_opengl_Window.cpp
@@ -420,7 +420,7 @@ static bool initWindowGLX13(JNIEnv *env, Display *disp, int screen, jstring titl
 	createWindow(env, disp, screen, vis_info, title, x, y, width, height, fscreen);
 	glx_window = glXCreateWindow(disp, configs[0], getCurrentWindow(), NULL);
 	makeCurrent();
-	if (ISDEBUGENABLED())
+	if (isDebugEnabled())
 		dumpVisualInfo(disp, vis_info);
 	XFree(configs);
 	XFree(vis_info);
@@ -433,7 +433,7 @@ static bool initWindowGLX(JNIEnv *env, Display *disp, int screen, jstring title,
 		throwException(env, "Could not find a matching pixel format");
 		return false;
 	}
-	if (ISDEBUGENABLED())
+	if (isDebugEnabled())
 		dumpVisualInfo(disp, vis_info);
 	context = glXCreateContext(disp, vis_info, NULL, True);
 	if (context == NULL) {
diff --git a/src/native/macosx/hid.cpp b/src/native/macosx/hid.cpp
index 56180947..e4794899 100644
--- a/src/native/macosx/hid.cpp
+++ b/src/native/macosx/hid.cpp
@@ -202,7 +202,7 @@ bool findDevice(hid_device_t *hid_dev, long device_usage_page, long device_usage
 			long usage_page;
 			if (getDictLong(dev_props, CFSTR(kIOHIDPrimaryUsageKey), &usage) &&
 			    getDictLong(dev_props, CFSTR(kIOHIDPrimaryUsagePageKey), &usage_page)) {
-				if (ISDEBUGENABLED()) {
+				if (isDebugEnabled()) {
 					printf("Considering device '");
 					printProperty(dev_props, CFSTR(kIOHIDProductKey));
 					printf("', usage page %ld usage %ld\n", usage_page, usage);
diff --git a/src/native/macosx/org_lwjgl_Sys.cpp b/src/native/macosx/org_lwjgl_Sys.cpp
index f76d3388..8e30e78e 100644
--- a/src/native/macosx/org_lwjgl_Sys.cpp
+++ b/src/native/macosx/org_lwjgl_Sys.cpp
@@ -88,6 +88,10 @@ JNIEXPORT jlong JNICALL Java_org_lwjgl_Sys_getTime
     return hires_timer;
 }
 
+JNIEXPORT jstring JNICALL Java_org_lwjgl_Sys_getNativeLibraryVersion(JNIEnv *env, jclass clazz) {
+	return getVersionString(env);
+}
+
 /*
  * Class:     org_lwjgl_Sys
  * Method:    setTime
diff --git a/src/native/win32/org_lwjgl_Sys.cpp b/src/native/win32/org_lwjgl_Sys.cpp
index c46eaa56..8ce62589 100644
--- a/src/native/win32/org_lwjgl_Sys.cpp
+++ b/src/native/win32/org_lwjgl_Sys.cpp
@@ -65,6 +65,10 @@ JNIEXPORT void JNICALL Java_org_lwjgl_Sys_setDebug(JNIEnv *env, jclass clazz, jb
 	setDebugEnabled(enabled == JNI_TRUE ? true : false);
 }
 
+JNIEXPORT jstring JNICALL Java_org_lwjgl_Sys_getNativeLibraryVersion(JNIEnv *env, jclass clazz) {
+	return getVersionString(env);
+}
+
 /*
  * Class:     org_lwjgl_Sys
  * Method:    getTime