Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -1814,13 +1814,14 @@
 	OBJCFLAGS="$OBJCFLAGS -Wunreachable-code"
 	AC_MSG_CHECKING(whether -Wunreachable-code can be used)
 	AC_COMPILE_IFELSE([
 		AC_LANG_SOURCE([[
 			#include <stdlib.h>
-	
-			typedef void *SEL;
-	
+
+			struct objc_selector;
+			typedef const struct objc_selector *SEL;
+
 			#ifdef __has_attribute
 			# if __has_attribute(objc_root_class)
 			__attribute__((__objc_root_class__))
 			# endif
 			#endif
@@ -1830,14 +1831,14 @@
 			    __attribute__((__noreturn__))
 			#endif
 			    ;
 			- (void)dealloc;
 			@end
-	
+
 			@interface Foo: Object
 			@end
-	
+
 			void
 			test(void)
 			{
 				if (sizeof(int) == 4)
 					__asm__ ("");
@@ -1844,11 +1845,11 @@
 				else if (sizeof(int) == 8)
 					__asm__ ("");
 				else
 					abort();
 			}
-	
+
 			/*
 			 * Unfortunately, this cannot be shorter, as it only
 			 * works when it is used inside a macro.
 			 */
 			#ifdef __clang__
@@ -1867,11 +1868,11 @@
 									\
 				abort();				\
 									\
 				[super dealloc];
 			#endif
-	
+
 			@implementation Foo
 			- (void)dealloc
 			{
 				OF_DEALLOC_UNSUPPORTED
 			}