diff --git a/base/allocator/allocator.gyp b/base/allocator/allocator.gyp
index 74e0a433176005..b744a3a472fb69 100644
--- a/base/allocator/allocator.gyp
+++ b/base/allocator/allocator.gyp
@@ -313,8 +313,7 @@
             'disable_debugallocation%': 0,
           },
           'conditions': [
-            # TODO(phajdan.jr): Also enable on Windows.
-            ['disable_debugallocation==0 and OS!="win"', {
+            ['disable_debugallocation==0', {
               'defines': [
                 # Use debugallocation for Debug builds to catch problems early
                 # and cleanly, http://crbug.com/30715 .
diff --git a/third_party/tcmalloc/chromium/src/config_win.h b/third_party/tcmalloc/chromium/src/config_win.h
index db4c51886c0366..e6506e44591421 100644
--- a/third_party/tcmalloc/chromium/src/config_win.h
+++ b/third_party/tcmalloc/chromium/src/config_win.h
@@ -74,7 +74,7 @@
 #undef HAVE_EXECINFO_H
 
 /* Define to 1 if you have the <fcntl.h> header file. */
-#undef HAVE_FCNTL_H
+#define HAVE_FCNTL_H 1
 
 /* Define to 1 if you have the <features.h> header file. */
 #undef HAVE_FEATURES_H
diff --git a/third_party/tcmalloc/chromium/src/debugallocation.cc b/third_party/tcmalloc/chromium/src/debugallocation.cc
index cccaf982b31154..7b09e412ec36b2 100644
--- a/third_party/tcmalloc/chromium/src/debugallocation.cc
+++ b/third_party/tcmalloc/chromium/src/debugallocation.cc
@@ -127,19 +127,16 @@ DEFINE_bool(symbolize_stacktrace,
             EnvToBool("TCMALLOC_SYMBOLIZE_STACKTRACE", true),
             "Symbolize the stack trace when provided (on some error exits)");
 
-// If we are LD_PRELOAD-ed against a non-pthreads app, then
-// pthread_once won't be defined.  We declare it here, for that
-// case (with weak linkage) which will cause the non-definition to
-// resolve to NULL.  We can then check for NULL or not in Instance.
-extern "C" int pthread_once(pthread_once_t *, void (*)(void))
-    ATTRIBUTE_WEAK;
-
 // ========================================================================= //
 
 // A safe version of printf() that does not do any allocation and
 // uses very little stack space.
 static void TracePrintf(int fd, const char *fmt, ...)
+#ifdef __GNUC__
   __attribute__ ((__format__ (__printf__, 2, 3)));
+#else
+  ;
+#endif
 
 // The do_* functions are defined in tcmalloc/tcmalloc.cc,
 // which is included before this file
@@ -624,9 +621,7 @@ class MallocBlock {
   }
 
   static void CheckForDanglingWrites(const MallocBlockQueueEntry& queue_entry) {
-    // Initialize the buffer if necessary.
-    if (pthread_once)
-      pthread_once(&deleted_buffer_initialized_, &InitDeletedBuffer);
+    perftools_pthread_once(&deleted_buffer_initialized_, &InitDeletedBuffer);
     if (!deleted_buffer_initialized_no_pthreads_) {
       // This will be the case on systems that don't link in pthreads,
       // including on FreeBSD where pthread_once has a non-zero address
diff --git a/third_party/tcmalloc/chromium/src/windows/port.h b/third_party/tcmalloc/chromium/src/windows/port.h
index e9a020656b36fd..c23810918592b7 100644
--- a/third_party/tcmalloc/chromium/src/windows/port.h
+++ b/third_party/tcmalloc/chromium/src/windows/port.h
@@ -49,6 +49,9 @@
 
 #ifdef _WIN32
 
+#ifndef NOMINMAX
+#define NOMINMAX             /* Do not define min and max macros. */
+#endif
 #ifndef WIN32_LEAN_AND_MEAN
 #define WIN32_LEAN_AND_MEAN  /* We always want minimal includes */
 #endif