diff --git a/properties.h b/properties.h
index 4f13a02..a9ac581 100644
--- a/properties.h
+++ b/properties.h
@@ -40,6 +40,50 @@ enum PropertyAttributeKind
 	OBJC_PR_setter    = (1<<7)
 };
 
+/**
+ * Flags in the second attributes field in declared properties.
+ * Note: This field replaces the old 'is synthesized' field and so these values
+ * are shifted left one from their values in clang.
+ */
+enum PropertyAttributeKind2
+{
+	/**
+	 * No extended attributes.
+	 */
+	OBJC_PR_noextattr         = 0,
+	/**
+	 * The property is synthesized.  This has no meaning in properties on
+	 * protocols.
+	 */
+	OBJC_PR_synthesized       = (1<<0),
+	/**
+	 * The property is dynamic (i.e. the implementation is inherited or
+	 * provided at run time).
+	 */
+	OBJC_PR_dynamic           = (1<<1),
+	/**
+	 * This property belongs to a protocol.
+	 */
+	OBJC_PR_protocol          = OBJC_PR_synthesized | OBJC_PR_dynamic,
+	/**
+	 * The property is atomic.
+	 */
+	OBJC_PR_atomic            = (1<<2),
+	/**
+	 * The property value is a zeroing weak reference.
+	 */
+	OBJC_PR_weak              = (1<<3),
+	/**
+	 * The property value is strong (retained).  Currently, this is equivalent
+	 * to the strong attribute.
+	 */
+	OBJC_PR_strong            = (1<<4),
+	/**
+	 * The property value is just copied.
+	 */
+	OBJC_PR_unsafe_unretained = (1<<5),
+};
+
 /**
  * Structure used for property enumeration.  Note that property enumeration is
  * currently quite broken on OS X, so achieving full compatibility there is
@@ -60,7 +104,17 @@ struct objc_property
 	/**
 	 * Flag set if the property is synthesized.
 	 */
-	const char isSynthesized;
+	char attributes2;
+	/**
+	 * Padding field.  These were implicit in the structure field alignment
+	 * (four more on 64-bit platforms), but we'll make them explicit now for
+	 * future use.
+	 */
+	char unused1;
+	/**
+	 * More padding.
+	 */
+	char unused2;
 	/**
 	 * Name of the getter for this property.
 	 */