diff --git a/libc/include/string.h b/libc/include/string.h
index d67928c..fffe136 100644
--- a/libc/include/string.h
+++ b/libc/include/string.h
@@ -44,6 +44,9 @@
 extern void*  memrchr(const void *, int, size_t) __purefunc;
 extern int    memcmp(const void *, const void *, size_t) __purefunc;
 extern void*  memcpy(void* __restrict, const void* __restrict, size_t);
+#if defined(__USE_GNU)
+extern void*  mempcpy(void* __restrict, const void* __restrict, size_t);
+#endif
 extern void*  memmove(void *, const void *, size_t);
 extern void*  memset(void *, int, size_t);
 extern void*  memmem(const void *, size_t, const void *, size_t) __purefunc;