diff --git a/libc/bionic/flockfile.cpp b/libc/bionic/flockfile.cpp
index db53828..db68801 100644
--- a/libc/bionic/flockfile.cpp
+++ b/libc/bionic/flockfile.cpp
@@ -36,12 +36,20 @@
 // struct __sfileext (see fileext.h).
 
 void flockfile(FILE* fp) {
+  if (!__sdidinit) {
+    __sinit();
+  }
+
   if (fp != nullptr) {
     pthread_mutex_lock(&_FLOCK(fp));
   }
 }
 
 int ftrylockfile(FILE* fp) {
+  if (!__sdidinit) {
+    __sinit();
+  }
+
   // 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) {
@@ -52,6 +60,10 @@
 }
 
 void funlockfile(FILE* fp) {
+  if (!__sdidinit) {
+    __sinit();
+  }
+
   if (fp != nullptr) {
     pthread_mutex_unlock(&_FLOCK(fp));
   }
diff --git a/libc/bionic/libc_init_common.cpp b/libc/bionic/libc_init_common.cpp
index 8f210ea..91e210e 100644
--- a/libc/bionic/libc_init_common.cpp
+++ b/libc/bionic/libc_init_common.cpp
@@ -54,7 +54,7 @@
 extern "C" int __system_properties_init(void);
 extern "C" int __set_tls(void* ptr);
 extern "C" int __set_tid_address(int* tid_address);
-extern "C" int __libc_init_stdio(void);
+extern "C" int __sinit(void);
 
 __LIBC_HIDDEN__ WriteProtected<libc_globals> __libc_globals;
 
@@ -134,9 +134,9 @@
   __pthread_internal_add(main_thread);
 
   __system_properties_init(); // Requires 'environ'.
-
-  // Initialize stdio to avoid data races caused by BSD-style lazy initialization.
-  __libc_init_stdio();
+  // Initialize stdio here to get rid of data races caused by lazy initialization.
+  // TODO: Remove other calls to __sinit().
+  __sinit();
 }
 
 __noreturn static void __early_abort(int line) {
diff --git a/libc/bionic/ndk_cruft.cpp b/libc/bionic/ndk_cruft.cpp
index 0af9d5b..d6b8e8f 100644
--- a/libc/bionic/ndk_cruft.cpp
+++ b/libc/bionic/ndk_cruft.cpp
@@ -286,13 +286,6 @@
   return r.rlim_cur;
 }
 
-// A leaked BSD stdio implementation detail that's now a no-op.
-// (GCC doesn't like 'extern "C"' on a definition.)
-extern "C" {
-void __sinit() {}
-int __sdidinit = 1;
-}
-
 // Only used by ftime, which was removed from POSIX 2008.
 struct timeb {
   time_t          time;
diff --git a/libc/stdio/findfp.c b/libc/stdio/findfp.c
index 4054d5f..2696cfd 100644
--- a/libc/stdio/findfp.c
+++ b/libc/stdio/findfp.c
@@ -44,6 +44,8 @@
 #define ALIGNBYTES (sizeof(uintptr_t) - 1)
 #define ALIGN(p) (((uintptr_t)(p) + ALIGNBYTES) &~ ALIGNBYTES)
 
+int	__sdidinit;
+
 #define	NDYNAMIC 10		/* add ten more whenever necessary */
 
 #define	std(flags, file) \
@@ -112,6 +114,9 @@
 	int n;
 	struct glue *g;
 
+	if (!__sdidinit)
+		__sinit();
+
 	_THREAD_PRIVATE_MUTEX_LOCK(__sfp_mutex);
 	for (g = &__sglue; g != NULL; g = g->next) {
 		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
@@ -144,21 +149,48 @@
 	return (fp);
 }
 
-static void __stdio_cleanup(void) {
+/*
+ * exit() and abort() call _cleanup() through the callback registered
+ * with __atexit_register_cleanup(), set whenever we open or buffer a
+ * file. This chicanery is done so that programs that do not use stdio
+ * need not link it all in.
+ *
+ * The name `_cleanup' is, alas, fairly well known outside stdio.
+ */
+void
+_cleanup(void)
+{
 	/* (void) _fwalk(fclose); */
 	(void) _fwalk(__sflush);		/* `cheating' */
 }
 
-void __libc_init_stdio(void) {
-	// Initialize stdin/stdout/stderr (for the recursive mutex). http://b/18208568.
+/*
+ * __sinit() is called whenever stdio's internal variables must be set up.
+ */
+void
+__sinit(void)
+{
+	_THREAD_PRIVATE_MUTEX(__sinit_mutex);
+
+	_THREAD_PRIVATE_MUTEX_LOCK(__sinit_mutex);
+	if (__sdidinit) {
+		/* bail out if caller lost the race */
+		_THREAD_PRIVATE_MUTEX_UNLOCK(__sinit_mutex);
+		return;
+	}
+
+	/* Initialize stdin/stdout/stderr (for the recursive mutex). http://b/18208568. */
 	for (size_t i = 0; i < 3; ++i) {
 		_FILEEXT_SETUP(__sF+i, __sFext+i);
 	}
-	// Initialize the pre-allocated (but initially unused) streams.
+	/* Initialize the pre-allocated (but initially unused) streams. */
 	for (size_t i = 0; i < FOPEN_MAX - 3; ++i) {
 		_FILEEXT_SETUP(usual+i, usualext+i);
 	}
 
-	// Make sure we clean up on exit.
-	__atexit_register_cleanup(__stdio_cleanup); /* conservative */
+	/* make sure we clean up on exit */
+	__atexit_register_cleanup(_cleanup); /* conservative */
+	__sdidinit = 1;
+
+	_THREAD_PRIVATE_MUTEX_UNLOCK(__sinit_mutex);
 }
diff --git a/libc/stdio/local.h b/libc/stdio/local.h
index db3068d..3ae7059 100644
--- a/libc/stdio/local.h
+++ b/libc/stdio/local.h
@@ -153,8 +153,10 @@
 __LIBC32_LEGACY_PUBLIC__ int __swsetup(FILE*);
 
 /* These were referenced by a couple of different pieces of middleware and the Crystax NDK. */
+__LIBC32_LEGACY_PUBLIC__ extern int __sdidinit;
 __LIBC32_LEGACY_PUBLIC__ int __sflags(const char*, int*);
 __LIBC32_LEGACY_PUBLIC__ FILE* __sfp(void);
+__LIBC32_LEGACY_PUBLIC__ void __sinit(void);
 __LIBC32_LEGACY_PUBLIC__ void __smakebuf(FILE*);
 
 /* These are referenced by the Greed for Glory franchise. */
@@ -168,6 +170,7 @@
 #pragma GCC visibility push(hidden)
 
 int	__sflush_locked(FILE *);
+void	_cleanup(void);
 int	__swhatbuf(FILE *, size_t *, int *);
 wint_t __fgetwc_unlock(FILE *);
 wint_t	__ungetwc(wint_t, FILE *);
@@ -234,10 +237,6 @@
 extern int __sfvwrite(FILE *, struct __suio *);
 wint_t __fputwc_unlock(wchar_t wc, FILE *fp);
 
-/* Remove the if (!__sdidinit) __sinit() idiom from untouched upstream stdio code. */
-extern void __sinit(void); // Not actually implemented.
-#define __sdidinit 1
-
 #pragma GCC visibility pop
 
 __END_DECLS
diff --git a/libc/stdio/refill.c b/libc/stdio/refill.c
index 5b0811f..e87c7b9 100644
--- a/libc/stdio/refill.c
+++ b/libc/stdio/refill.c
@@ -51,6 +51,11 @@
 int
 __srefill(FILE *fp)
 {
+
+	/* make sure stdio is set up */
+	if (!__sdidinit)
+		__sinit();
+
 	fp->_r = 0;		/* largely a convenience for callers */
 
 #if !defined(__ANDROID__)