diff --git a/libc/Android.bp b/libc/Android.bp
index 1e65fea..e5a7454 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -1088,7 +1088,6 @@
         "bionic/ffs.cpp",
         "bionic/fgetxattr.cpp",
         "bionic/flistxattr.cpp",
-        "bionic/flockfile.cpp",
         "bionic/fpclassify.cpp",
         "bionic/fsetxattr.cpp",
         "bionic/ftruncate.cpp",
diff --git a/libc/bionic/flockfile.cpp b/libc/bionic/flockfile.cpp
deleted file mode 100644
index db53828..0000000
--- a/libc/bionic/flockfile.cpp
+++ /dev/null
@@ -1,58 +0,0 @@
-/*
- * Copyright (C) 2008 The Android Open Source Project
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *  * Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- *  * Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in
- *    the documentation and/or other materials provided with the
- *    distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
- * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include <errno.h>
-#include <stdio.h>
-
-#include "local.h"
-
-// We can't use the OpenBSD implementation which uses kernel-specific
-// APIs not available on Linux. Instead we use a pthread_mutex_t within
-// struct __sfileext (see fileext.h).
-
-void flockfile(FILE* fp) {
-  if (fp != nullptr) {
-    pthread_mutex_lock(&_FLOCK(fp));
-  }
-}
-
-int ftrylockfile(FILE* fp) {
-  // The specification for ftrylockfile() says it returns 0 on success,
-  // or non-zero on error. So return an errno code directly on error.
-  if (fp == nullptr) {
-    return EINVAL;
-  }
-
-  return pthread_mutex_trylock(&_FLOCK(fp));
-}
-
-void funlockfile(FILE* fp) {
-  if (fp != nullptr) {
-    pthread_mutex_unlock(&_FLOCK(fp));
-  }
-}
diff --git a/libc/stdio/local.h b/libc/stdio/local.h
index 6ffda49..2fc12a0 100644
--- a/libc/stdio/local.h
+++ b/libc/stdio/local.h
@@ -170,7 +170,6 @@
 #define _EXT(fp) __BIONIC_CAST(reinterpret_cast, struct __sfileext*, (fp)->_ext._base)
 
 #define _UB(fp) _EXT(fp)->_ub
-#define _FLOCK(fp) _EXT(fp)->_lock
 
 #define _FILEEXT_SETUP(fp, fext)                                              \
   do {                                                                        \
diff --git a/libc/stdio/stdio.cpp b/libc/stdio/stdio.cpp
index 27813a6..4f12fd0 100644
--- a/libc/stdio/stdio.cpp
+++ b/libc/stdio/stdio.cpp
@@ -197,7 +197,7 @@
 	fp->_lb._size = 0;
 
 	memset(_EXT(fp), 0, sizeof(struct __sfileext));
-	_FLOCK(fp) = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
+	_EXT(fp)->_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
 	_EXT(fp)->_caller_handles_locking = false;
 
 	// Caller sets cookie, _read/_write etc.
@@ -1239,6 +1239,23 @@
   return __FILE_close(fp);
 }
 
+void flockfile(FILE* fp) {
+  CHECK_FP(fp);
+  pthread_mutex_lock(&_EXT(fp)->_lock);
+}
+
+int ftrylockfile(FILE* fp) {
+  CHECK_FP(fp);
+  // The specification for ftrylockfile() says it returns 0 on success,
+  // or non-zero on error. We don't bother canonicalizing to 0/-1...
+  return pthread_mutex_trylock(&_EXT(fp)->_lock);
+}
+
+void funlockfile(FILE* fp) {
+  CHECK_FP(fp);
+  pthread_mutex_unlock(&_EXT(fp)->_lock);
+}
+
 namespace {
 
 namespace phony {