diff --git a/libc/bionic/getcwd.cpp b/libc/bionic/getcwd.cpp
index c2a7e23..50487ec 100644
--- a/libc/bionic/getcwd.cpp
+++ b/libc/bionic/getcwd.cpp
@@ -26,7 +26,6 @@
  * SUCH DAMAGE.
  */
 
-#undef _FORTIFY_SOURCE
 #include <errno.h>
 #include <malloc.h>
 #include <string.h>
diff --git a/libc/bionic/poll.cpp b/libc/bionic/poll.cpp
index eded56a..dbc9584 100644
--- a/libc/bionic/poll.cpp
+++ b/libc/bionic/poll.cpp
@@ -26,7 +26,6 @@
  * SUCH DAMAGE.
  */
 
-#undef _FORTIFY_SOURCE
 #include <errno.h>
 #include <sys/poll.h>
 #include <sys/select.h>
diff --git a/libc/bionic/readlink.cpp b/libc/bionic/readlink.cpp
index a53f933..3bb7bc1 100644
--- a/libc/bionic/readlink.cpp
+++ b/libc/bionic/readlink.cpp
@@ -26,8 +26,6 @@
  * SUCH DAMAGE.
  */
 
-#undef _FORTIFY_SOURCE
-
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/types.h>
diff --git a/libc/bionic/recv.cpp b/libc/bionic/recv.cpp
index 061cd46..60f264d 100644
--- a/libc/bionic/recv.cpp
+++ b/libc/bionic/recv.cpp
@@ -26,7 +26,6 @@
  * SUCH DAMAGE.
  */
 
-#undef _FORTIFY_SOURCE
 #include <sys/socket.h>
 
 ssize_t recv(int socket, void *buf, size_t len, int flags) {
diff --git a/libc/bionic/strchr.cpp b/libc/bionic/strchr.cpp
index 5bd3f19..fd8a924 100644
--- a/libc/bionic/strchr.cpp
+++ b/libc/bionic/strchr.cpp
@@ -27,7 +27,6 @@
  * SUCH DAMAGE.
  */
 
-#undef _FORTIFY_SOURCE
 #include <string.h>
 
 char* strchr(const char* p, int ch) {
diff --git a/libc/bionic/strrchr.cpp b/libc/bionic/strrchr.cpp
index 3fdb47c..b6c40f4 100644
--- a/libc/bionic/strrchr.cpp
+++ b/libc/bionic/strrchr.cpp
@@ -27,7 +27,6 @@
  * SUCH DAMAGE.
  */
 
-#undef _FORTIFY_SOURCE
 #include <string.h>
 
 char* strrchr(const char* p, int ch) {
diff --git a/libc/include/bits/lockf.h b/libc/include/bits/lockf.h
index c24f18b..a8e273e 100644
--- a/libc/include/bits/lockf.h
+++ b/libc/include/bits/lockf.h
@@ -39,11 +39,7 @@
 
 __BEGIN_DECLS
 
-#if defined(__USE_FILE_OFFSET64)
-int lockf(int, int, off_t) __RENAME(lockf64) __INTRODUCED_IN(24);
-#else
-int lockf(int, int, off_t) __INTRODUCED_IN(24);
-#endif
+int lockf(int, int, off_t) __RENAME_IF_FILE_OFFSET64(lockf64) __INTRODUCED_IN(24);
 int lockf64(int, int, off64_t) __INTRODUCED_IN(24);
 
 __END_DECLS
diff --git a/libc/include/fcntl.h b/libc/include/fcntl.h
index c98022c..f27efdf 100644
--- a/libc/include/fcntl.h
+++ b/libc/include/fcntl.h
@@ -71,8 +71,7 @@
 
 int creat(const char*, mode_t);
 int creat64(const char*, mode_t) __INTRODUCED_IN(21);
-int openat(int, const char*, int, ...) __overloadable
-        __RENAME_CLANG(openat);
+int openat(int, const char*, int, ...) __overloadable __RENAME_CLANG(openat);
 int openat64(int, const char*, int, ...) __INTRODUCED_IN(21);
 int open(const char*, int, ...) __overloadable __RENAME_CLANG(open);
 int open64(const char*, int, ...) __INTRODUCED_IN(21);
@@ -80,17 +79,11 @@
 ssize_t tee(int, int, size_t, unsigned int) __INTRODUCED_IN(21);
 ssize_t vmsplice(int, const struct iovec*, size_t, unsigned int) __INTRODUCED_IN(21);
 
-#if defined(__USE_FILE_OFFSET64)
-int fallocate(int, int, off_t, off_t) __RENAME(fallocate64) __INTRODUCED_IN(21);
-int posix_fadvise(int, off_t, off_t, int) __RENAME(posix_fadvise64) __INTRODUCED_IN(21);
-int posix_fallocate(int, off_t, off_t) __RENAME(posix_fallocate64) __INTRODUCED_IN(21);
-#else
-int fallocate(int, int, off_t, off_t) __INTRODUCED_IN(21);
-int posix_fadvise(int, off_t, off_t, int) __INTRODUCED_IN(21);
-int posix_fallocate(int, off_t, off_t) __INTRODUCED_IN(21);
-#endif
+int fallocate(int, int, off_t, off_t) __RENAME_IF_FILE_OFFSET64(fallocate64) __INTRODUCED_IN(21);
 int fallocate64(int, int, off64_t, off64_t) __INTRODUCED_IN(21);
+int posix_fadvise(int, off_t, off_t, int) __RENAME_IF_FILE_OFFSET64(posix_fadvise64) __INTRODUCED_IN(21);
 int posix_fadvise64(int, off64_t, off64_t, int) __INTRODUCED_IN(21);
+int posix_fallocate(int, off_t, off_t) __RENAME_IF_FILE_OFFSET64(posix_fallocate64) __INTRODUCED_IN(21);
 int posix_fallocate64(int, off64_t, off64_t) __INTRODUCED_IN(21);
 
 #if defined(__USE_GNU)
diff --git a/libc/include/sys/cdefs.h b/libc/include/sys/cdefs.h
index 307545c..dd5b345 100644
--- a/libc/include/sys/cdefs.h
+++ b/libc/include/sys/cdefs.h
@@ -237,6 +237,11 @@
 /* _FILE_OFFSET_BITS 64 support. */
 #if !defined(__LP64__) && defined(_FILE_OFFSET_BITS) && _FILE_OFFSET_BITS == 64
 #define __USE_FILE_OFFSET64 1
+/*
+ * Note that __RENAME_IF_FILE_OFFSET64 is only valid if the off_t and off64_t
+ * functions were both added at the same API level because if you use this,
+ * you only have one declaration to attach __INTRODUCED_IN to.
+ */
 #define __RENAME_IF_FILE_OFFSET64(func) __RENAME(func)
 #else
 #define __RENAME_IF_FILE_OFFSET64(func)
diff --git a/libc/include/sys/uio.h b/libc/include/sys/uio.h
index 2611774..b166277 100644
--- a/libc/include/sys/uio.h
+++ b/libc/include/sys/uio.h
@@ -38,13 +38,8 @@
 ssize_t writev(int, const struct iovec*, int);
 
 #if defined(__USE_GNU)
-#if defined(__USE_FILE_OFFSET64)
-ssize_t preadv(int, const struct iovec*, int, off_t) __RENAME(preadv64) __INTRODUCED_IN(24);
-ssize_t pwritev(int, const struct iovec*, int, off_t) __RENAME(pwritev64) __INTRODUCED_IN(24);
-#else
-ssize_t preadv(int, const struct iovec*, int, off_t) __INTRODUCED_IN(24);
-ssize_t pwritev(int, const struct iovec*, int, off_t) __INTRODUCED_IN(24);
-#endif
+ssize_t preadv(int, const struct iovec*, int, off_t) __RENAME_IF_FILE_OFFSET64(preadv64) __INTRODUCED_IN(24);
+ssize_t pwritev(int, const struct iovec*, int, off_t) __RENAME_IF_FILE_OFFSET64(pwritev64) __INTRODUCED_IN(24);
 ssize_t preadv64(int, const struct iovec*, int, off64_t) __INTRODUCED_IN(24);
 ssize_t pwritev64(int, const struct iovec*, int, off64_t) __INTRODUCED_IN(24);
 #endif