diff --git a/GNUmakefile b/GNUmakefile
index 542fc91..c1c1e5e 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -5,12 +5,14 @@ LIBRARY_NAME = libobjc
 libobjc_VERSION = 4
 
 libobjc_OBJC_FILES = \
-	blocks_runtime.m\
-	linking.m\
-	mutation.m\
+	NSBlocks.m\
 	NXConstStr.m\
 	Object.m\
 	Protocol.m\
+	blocks_runtime.m\
+	linking.m\
+	mutation.m\
+	properties.m\
 	sync.m
 
 
@@ -31,6 +33,7 @@ libobjc_C_FILES = \
 	selector.c\
 	sendmsg.c\
 	thr.c
+
 libobjc_HEADER_FILES_DIR = objc
 libobjc_HEADER_FILES_INSTALL_DIR = objc
 libobjc_HEADER_FILES = \
diff --git a/NSBlocks.m b/NSBlocks.m
new file mode 100644
index 0000000..183c494
--- /dev/null
+++ b/NSBlocks.m
@@ -0,0 +1,56 @@
+#import <Foundation/NSObject.h>
+#import "objc/runtime.h"
+#import "objc/blocks_runtime.h"
+#include <assert.h>
+
+struct objc_class _NSConcreteGlobalBlock;
+struct objc_class _NSConcreteStackBlock;
+
+@interface NSBlock : NSObject @end
+
+void __objc_update_dispatch_table_for_class(Class);
+extern struct sarray *__objc_uninstalled_dtable;
+extern objc_mutex_t __objc_runtime_mutex;
+static void createNSBlockSubclass(Class newClass, char *name)
+{
+	Class superclass = [NSBlock class];
+	// Create the metaclass
+	Class metaClass = calloc(1, sizeof(struct objc_class));
+
+	// Initialize the metaclass
+	metaClass->class_pointer = superclass->class_pointer;
+	metaClass->super_class = superclass->class_pointer->super_class;
+	metaClass->info = _CLS_META;
+	metaClass->dtable = __objc_uninstalled_dtable;
+
+	// Set up the new class
+	newClass->class_pointer = metaClass;
+	newClass->super_class = superclass;
+	newClass->name = name;
+	newClass->info = _CLS_CLASS;
+	newClass->dtable = __objc_uninstalled_dtable;
+
+	// Initialize the dispatch table for the class and metaclass.
+	__objc_update_dispatch_table_for_class(metaClass);
+	__objc_update_dispatch_table_for_class(newClass);
+	CLS_SETINITIALIZED(metaClass);
+	CLS_SETINITIALIZED(newClass);
+	CLS_SETRESOLV(metaClass);
+	CLS_SETRESOLV(newClass);
+	// Add pointer from super class
+	objc_mutex_lock(__objc_runtime_mutex);
+	newClass->sibling_class = newClass->super_class->subclass_list;
+	newClass->super_class->subclass_list = newClass;
+	metaClass->sibling_class = metaClass->super_class->subclass_list;
+	metaClass->super_class->subclass_list = metaClass;
+	objc_mutex_unlock(__objc_runtime_mutex);
+}
+
+@implementation NSBlock
++ (void)load
+{
+	createNSBlockSubclass(&_NSConcreteGlobalBlock, "_NSConcreteGlobalBlockPrivate");
+	createNSBlockSubclass(&_NSConcreteStackBlock, "_NSConcreteStackBlockPrivate");
+}
+@end
+
diff --git a/exception.c b/exception.c
index 5100a23..7c57dfa 100644
--- a/exception.c
+++ b/exception.c
@@ -27,6 +27,10 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 //#include <unwind.h>
 #include "unwind-pe.h"
 
+void (*__objc_unhandled_exception)(id) = 0;
+
+__attribute__((weak)) int main(void);
+
 
 #ifdef __ARM_EABI_UNWINDER__
 
@@ -451,6 +455,13 @@ PERSONALITY_FUNCTION (int version,
  install_context:
   if (saw_cleanup == 0)
     {
+      if (_Unwind_GetRegionStart(context) == (int)main)
+        {
+          if (__objc_unhandled_exception)
+            {
+              __objc_unhandled_exception(xh->value);
+            }
+        }
       return_object = xh->value;
       if (!(actions & _UA_SEARCH_PHASE))
 	_Unwind_DeleteException(&xh->base);
diff --git a/objc/runtime.h b/objc/runtime.h
index a3e0c24..5cfbb41 100644
--- a/objc/runtime.h
+++ b/objc/runtime.h
@@ -315,6 +315,12 @@ id (*objc_proxy_lookup)(id receiver, SEL op) OBJC_NONPORTABLE;
  */
 struct objc_slot *(*objc_msg_forward3)(id receiver, SEL op) OBJC_NONPORTABLE;
 
+/**
+ * Runtime hook for unhandled exceptions.  This is called if an exception is
+ * not caught.
+ */
+void (*__objc_unhandled_exception)(id);
+
 // Global self so that self is a valid symbol everywhere.  Will be replaced by
 // a real self in an inner scope if there is one.
 static const id self = nil;
diff --git a/properties.m b/properties.m
new file mode 100644
index 0000000..eaff548
--- /dev/null
+++ b/properties.m
@@ -0,0 +1,47 @@
+#include "objc/runtime.h"
+
+// Subset of NSObject interface needed for properties.
+@interface NSObject {}
+- (id)retain;
+- (id)copy;
+- (id)autorelease;
+- (void)release;
+@end
+
+id objc_getProperty(id obj, SEL _cmd, ptrdiff_t offset, BOOL isAtomic)
+{
+	if (isAtomic)
+	{
+		@synchronized(obj) {
+			return objc_getProperty(obj, _cmd, offset, NO);
+		}
+	}
+	char *addr = (char*)obj;
+	addr += offset;
+	id ret = *(id*)addr;
+	return [[ret retain] autorelease];
+}
+
+void objc_setProperty(id obj, SEL _cmd, ptrdiff_t offset, id arg, BOOL isAtomic, BOOL isCopy)
+{
+	if (isAtomic)
+	{
+		@synchronized(obj) {
+			objc_setProperty(obj, _cmd, offset, arg, NO, isCopy);
+			return;
+		}
+	}
+	if (isCopy)
+	{
+		arg = [arg copy];
+	}
+	else
+	{
+		arg = [arg retain];
+	}
+	char *addr = (char*)obj;
+	addr += offset;
+	id old = *(id*)addr;
+	*(id*)addr = arg;
+	[old release];
+}
diff --git a/sendmsg.c b/sendmsg.c
index eb9bff1..f1fb7cc 100644
--- a/sendmsg.c
+++ b/sendmsg.c
@@ -606,7 +606,7 @@ static void merge_methods_from_superclass (Class class)
           method_list = method_list->method_next;
         }
     } 
-  while (super = super->super_class);
+  while ((super = super->super_class));
   if (class->subclass_list)        /* Traverse subclasses */
     for (Class next = class->subclass_list; next; next = next->sibling_class)
       merge_methods_from_superclass (next);