diff --git a/libc/include/fcntl.h b/libc/include/fcntl.h
index 4ef894b..1ec932b 100644
--- a/libc/include/fcntl.h
+++ b/libc/include/fcntl.h
@@ -149,7 +149,7 @@
  *
  * Available since API level 21.
  */
-ssize_t splice(int __in_fd, off64_t* _Null_unspecified __in_offset, int __out_fd, off64_t* _Null_unspecified __out_offset, size_t __length, unsigned int __flags) __INTRODUCED_IN(21);
+ssize_t splice(int __in_fd, off64_t* __BIONIC_COMPLICATED_NULLNESS __in_offset, int __out_fd, off64_t* __BIONIC_COMPLICATED_NULLNESS __out_offset, size_t __length, unsigned int __flags) __INTRODUCED_IN(21);
 
 /**
  * [tee(2)](http://man7.org/linux/man-pages/man2/tee.2.html)
diff --git a/libc/include/regex.h b/libc/include/regex.h
index be1418e..be33819 100644
--- a/libc/include/regex.h
+++ b/libc/include/regex.h
@@ -49,8 +49,8 @@
 typedef struct {
 	int re_magic;
 	size_t re_nsub;		/* number of parenthesized subexpressions */
-	const char * _Null_unspecified re_endp;	/* end pointer for REG_PEND */
-	struct re_guts * _Null_unspecified re_g;	/* none of your business :-) */
+	const char * __BIONIC_COMPLICATED_NULLNESS re_endp;	/* end pointer for REG_PEND */
+	struct re_guts * __BIONIC_COMPLICATED_NULLNESS re_g;	/* none of your business :-) */
 } regex_t;
 
 typedef struct {
diff --git a/libc/include/sys/cdefs.h b/libc/include/sys/cdefs.h
index 5b9d99b..484757e 100644
--- a/libc/include/sys/cdefs.h
+++ b/libc/include/sys/cdefs.h
@@ -63,6 +63,14 @@
 #define __BIONIC_ALIGN(__value, __alignment) (((__value) + (__alignment)-1) & ~((__alignment)-1))
 
 /*
+ * The nullness constraints of this parameter or return value are
+ * quite complex. This is used to highlight spots where developers
+ * are encouraged to read relevant manuals or code to understand
+ * the full picture of nullness for this pointer.
+ */
+#define __BIONIC_COMPLICATED_NULLNESS _Null_unspecified
+
+/*
  * The __CONCAT macro is used to concatenate parts of symbol names, e.g.
  * with "#define OLD(foo) __CONCAT(old,foo)", OLD(foo) produces oldfoo.
  * The __CONCAT macro is a bit tricky -- make sure you don't put spaces