diff --git a/libc/include/strings.h b/libc/include/strings.h
index ff6b925..2f4f764 100644
--- a/libc/include/strings.h
+++ b/libc/include/strings.h
@@ -61,13 +61,13 @@
 
 /** Deprecated. Use memmove() instead. */
 #define bcopy(b1, b2, len) __bionic_bcopy((b1), (b2), (len))
-static __inline__ __always_inline void __bionic_bcopy(const void* b1, void* b2, size_t len) {
+static __inline__ __always_inline void __bionic_bcopy(const void* _Nonnull b1, void* _Nonnull b2, size_t len) {
   __builtin_memmove(b2, b1, len);
 }
 
 /** Deprecated. Use memset() instead. */
 #define bzero(b, len) __bionic_bzero((b), (len))
-static __inline__ __always_inline void __bionic_bzero(void* b, size_t len) {
+static __inline__ __always_inline void __bionic_bzero(void* _Nonnull b, size_t len) {
   __builtin_memset(b, 0, len);
 }