diff --git a/libc/include/errno.h b/libc/include/errno.h
index 8b2e8ed..3f4cff9 100644
--- a/libc/include/errno.h
+++ b/libc/include/errno.h
@@ -41,7 +41,7 @@
 #endif
 
 /* internal function returning the address of the thread-specific errno */
-volatile int* __errno(void) __pure2;
+volatile int* __errno(void) __attribute_const__;
 
 /* a macro expanding to the errno l-value */
 #define  errno   (*__errno())