diff --git a/arch/x86/include/asm/prctl.h b/arch/x86/include/asm/prctl.h
index fe681147a4f..a8894647dd9 100644
--- a/arch/x86/include/asm/prctl.h
+++ b/arch/x86/include/asm/prctl.h
@@ -6,5 +6,8 @@
 #define ARCH_GET_FS 0x1003
 #define ARCH_GET_GS 0x1004
 
+#ifdef CONFIG_X86_64
+extern long sys_arch_prctl(int, unsigned long);
+#endif /* CONFIG_X86_64 */
 
 #endif /* _ASM_X86_PRCTL_H */
diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h
index 2ed3f0f44ff..59555f48bf4 100644
--- a/arch/x86/include/asm/system.h
+++ b/arch/x86/include/asm/system.h
@@ -17,12 +17,12 @@
 # define AT_VECTOR_SIZE_ARCH 1
 #endif
 
-#ifdef CONFIG_X86_32
-
 struct task_struct; /* one of the stranger aspects of C forward declarations */
 struct task_struct *__switch_to(struct task_struct *prev,
 				struct task_struct *next);
 
+#ifdef CONFIG_X86_32
+
 /*
  * Saving eflags is important. It switches not only IOPL between tasks,
  * it also protects other tasks from NT leaking through sysenter etc.