diff --git a/include/grpc/support/log_win32.h b/include/grpc/support/log_win32.h
index ea6b16d..3546266 100644
--- a/include/grpc/support/log_win32.h
+++ b/include/grpc/support/log_win32.h
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -42,7 +42,7 @@
  * formatted error message, corresponding to the error messageid.
  * Use in conjunction with GetLastError() et al.
  */
-char *gpr_format_message(DWORD messageid);
+char *gpr_format_message(int messageid);
 
 #ifdef __cplusplus
 }
diff --git a/include/grpc/support/thd.h b/include/grpc/support/thd.h
index 58b8a83..56185cc 100644
--- a/include/grpc/support/thd.h
+++ b/include/grpc/support/thd.h
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -48,7 +48,7 @@
 extern "C" {
 #endif
 
-typedef uint64_t gpr_thd_id;
+typedef uintptr_t gpr_thd_id;
 
 /* Thread creation options. */
 typedef struct {
diff --git a/src/core/iomgr/iocp_windows.c b/src/core/iomgr/iocp_windows.c
index d3868ce..6cbe7d2 100644
--- a/src/core/iomgr/iocp_windows.c
+++ b/src/core/iomgr/iocp_windows.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -67,7 +67,7 @@
     return 0;
   }
   timeout = gpr_time_sub(deadline, now);
-  return gpr_time_to_millis(gpr_time_add(
+  return (DWORD)gpr_time_to_millis(gpr_time_add(
       timeout, gpr_time_from_nanos(GPR_NS_PER_MS - 1, GPR_TIMESPAN)));
 }
 
@@ -179,11 +179,9 @@
 static void socket_notify_on_iocp(grpc_exec_ctx *exec_ctx,
                                   grpc_winsocket *socket, grpc_closure *closure,
                                   grpc_winsocket_callback_info *info) {
-  int run_now = 0;
   GPR_ASSERT(info->closure == NULL);
   gpr_mu_lock(&socket->state_mu);
   if (info->has_pending_iocp) {
-    run_now = 1;
     info->has_pending_iocp = 0;
     grpc_exec_ctx_enqueue(exec_ctx, closure, 1);
   } else {
diff --git a/src/core/iomgr/pollset_windows.c b/src/core/iomgr/pollset_windows.c
index deb6615..bfd9e69 100644
--- a/src/core/iomgr/pollset_windows.c
+++ b/src/core/iomgr/pollset_windows.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -81,15 +81,6 @@
   }
 }
 
-static void push_back_worker(grpc_pollset_worker *root,
-                             grpc_pollset_worker_link_type type,
-                             grpc_pollset_worker *worker) {
-  worker->links[type].next = root;
-  worker->links[type].prev = worker->links[type].next->links[type].prev;
-  worker->links[type].prev->links[type].next =
-      worker->links[type].next->links[type].prev = worker;
-}
-
 static void push_front_worker(grpc_pollset_worker *root,
                               grpc_pollset_worker_link_type type,
                               grpc_pollset_worker *worker) {
diff --git a/src/core/iomgr/sockaddr_win32.h b/src/core/iomgr/sockaddr_win32.h
index fe2be99..8e3946a 100644
--- a/src/core/iomgr/sockaddr_win32.h
+++ b/src/core/iomgr/sockaddr_win32.h
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -38,9 +38,4 @@
 #include <ws2tcpip.h>
 #include <mswsock.h>
 
-#ifdef __MINGW32__
-/* mingw seems to be missing that definition. */
-const char *inet_ntop(int af, const void *src, char *dst, socklen_t size);
-#endif
-
 #endif /* GRPC_INTERNAL_CORE_IOMGR_SOCKADDR_WIN32_H */
diff --git a/src/core/iomgr/tcp_server_windows.c b/src/core/iomgr/tcp_server_windows.c
index 8ee8149..00d381f 100644
--- a/src/core/iomgr/tcp_server_windows.c
+++ b/src/core/iomgr/tcp_server_windows.c
@@ -531,7 +531,7 @@
   for (sp = s->head; sp && port_index != 0; sp = sp->next, --port_index)
     ;
   if (sp) {
-    return _open_osfhandle(sp->socket->socket, 0);
+    return _open_osfhandle((intptr_t)sp->socket->socket, 0);
   } else {
     return -1;
   }
diff --git a/src/core/iomgr/tcp_windows.c b/src/core/iomgr/tcp_windows.c
index cc7f7ff..d3f080c 100644
--- a/src/core/iomgr/tcp_windows.c
+++ b/src/core/iomgr/tcp_windows.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -143,10 +143,7 @@
   grpc_closure *cb = tcp->read_cb;
   grpc_winsocket *socket = tcp->socket;
   gpr_slice sub;
-  gpr_slice *slice = NULL;
-  size_t nslices = 0;
   grpc_winsocket_callback_info *info = &socket->read_info;
-  int do_abort = 0;
 
   if (success) {
     if (socket->read_info.wsa_error != 0 && !tcp->shutting_down) {
@@ -238,7 +235,6 @@
   grpc_winsocket *handle = tcp->socket;
   grpc_winsocket_callback_info *info = &handle->write_info;
   grpc_closure *cb;
-  int do_abort = 0;
 
   gpr_mu_lock(&tcp->mu);
   cb = tcp->write_cb;
diff --git a/src/core/support/env_win32.c b/src/core/support/env_win32.c
index 6b1ff10..1025828 100644
--- a/src/core/support/env_win32.c
+++ b/src/core/support/env_win32.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -38,7 +38,12 @@
 #include "src/core/support/env.h"
 #include "src/core/support/string.h"
 
+#ifdef __MINGW32__
+errno_t getenv_s(size_t *size_needed, char *buffer, size_t size,
+                 const char *varname);
+#else
 #include <stdlib.h>
+#endif
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
@@ -47,14 +52,17 @@
 char *gpr_getenv(const char *name) {
   size_t size;
   char *result = NULL;
-  char *duplicated;
   errno_t err;
 
-  err = _dupenv_s(&result, &size, name);
-  if (err) return NULL;
-  duplicated = gpr_strdup(result);
-  free(result);
-  return duplicated;
+  err = getenv_s(&size, NULL, 0, name);
+  if (err || (size == 0)) return NULL;
+  result = gpr_malloc(size);
+  err = getenv_s(&size, result, size, name);
+  if (err) {
+    gpr_free(result);
+    return NULL;
+  }
+  return result;
 }
 
 void gpr_setenv(const char *name, const char *value) {
diff --git a/src/core/support/log_win32.c b/src/core/support/log_win32.c
index 40adcd1..e18e667 100644
--- a/src/core/support/log_win32.c
+++ b/src/core/support/log_win32.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -109,13 +109,13 @@
   fflush(stderr);
 }
 
-char *gpr_format_message(DWORD messageid) {
+char *gpr_format_message(int messageid) {
   LPTSTR tmessage;
   char *message;
   DWORD status = FormatMessage(
       FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
           FORMAT_MESSAGE_IGNORE_INSERTS,
-      NULL, messageid, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+      NULL, (DWORD)messageid, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
       (LPTSTR)(&tmessage), 0, NULL);
   if (status == 0) return gpr_strdup("Unable to retrieve error string");
   message = gpr_tchar_to_char(tmessage);
diff --git a/src/core/support/string_win32.c b/src/core/support/string_win32.c
index 914ba87..3b1f702 100644
--- a/src/core/support/string_win32.c
+++ b/src/core/support/string_win32.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -85,8 +85,8 @@
 gpr_char_to_tchar(LPCSTR input) {
   LPTSTR ret;
   int needed = MultiByteToWideChar(CP_UTF8, 0, input, -1, NULL, 0);
-  if (needed == 0) return NULL;
-  ret = gpr_malloc(needed * sizeof(TCHAR));
+  if (needed <= 0) return NULL;
+  ret = gpr_malloc((unsigned)needed * sizeof(TCHAR));
   MultiByteToWideChar(CP_UTF8, 0, input, -1, ret, needed);
   return ret;
 }
@@ -95,8 +95,8 @@
 gpr_tchar_to_char(LPCTSTR input) {
   LPSTR ret;
   int needed = WideCharToMultiByte(CP_UTF8, 0, input, -1, NULL, 0, NULL, NULL);
-  if (needed == 0) return NULL;
-  ret = gpr_malloc(needed);
+  if (needed <= 0) return NULL;
+  ret = gpr_malloc((unsigned)needed);
   WideCharToMultiByte(CP_UTF8, 0, input, -1, ret, needed, NULL, NULL);
   return ret;
 }
diff --git a/src/core/support/sync_win32.c b/src/core/support/sync_win32.c
index 51a082b..84d412a 100644
--- a/src/core/support/sync_win32.c
+++ b/src/core/support/sync_win32.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -94,7 +94,11 @@
     if (now_ms >= deadline_ms) {
       timeout = 1;
     } else {
-      timeout_max_ms = (DWORD)min(deadline_ms - now_ms, INFINITE - 1);
+      if ((deadline_ms - now_ms) >= INFINITE) {
+        timeout_max_ms = INFINITE - 1;
+      } else {
+        timeout_max_ms = (DWORD)(deadline_ms - now_ms);
+      }
       timeout = (SleepConditionVariableCS(cv, &mu->cs, timeout_max_ms) == 0 &&
                  GetLastError() == ERROR_TIMEOUT);
     }
diff --git a/src/core/support/time_win32.c b/src/core/support/time_win32.c
index 2bed0f6..8af957e 100644
--- a/src/core/support/time_win32.c
+++ b/src/core/support/time_win32.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -37,9 +37,12 @@
 
 #ifdef GPR_WIN32
 
+#include <grpc/support/log.h>
 #include <grpc/support/time.h>
 #include <src/core/support/time_precise.h>
 #include <sys/timeb.h>
+#include <process.h>
+#include <limits.h>
 
 #include "src/core/support/block_annotate.h"
 
@@ -50,11 +53,12 @@
   LARGE_INTEGER frequency;
   QueryPerformanceFrequency(&frequency);
   QueryPerformanceCounter(&g_start_time);
-  g_time_scale = 1.0 / frequency.QuadPart;
+  g_time_scale = 1.0 / (double)frequency.QuadPart;
 }
 
 gpr_timespec gpr_now(gpr_clock_type clock) {
   gpr_timespec now_tv;
+  LONGLONG diff;
   struct _timeb now_tb;
   LARGE_INTEGER timestamp;
   double now_dbl;
@@ -68,10 +72,14 @@
     case GPR_CLOCK_MONOTONIC:
     case GPR_CLOCK_PRECISE:
       QueryPerformanceCounter(&timestamp);
-      now_dbl = (timestamp.QuadPart - g_start_time.QuadPart) * g_time_scale;
+      diff = timestamp.QuadPart - g_start_time.QuadPart;
+      now_dbl = (double)diff * g_time_scale;
       now_tv.tv_sec = (int64_t)now_dbl;
       now_tv.tv_nsec = (int32_t)((now_dbl - (double)now_tv.tv_sec) * 1e9);
       break;
+    case GPR_TIMESPAN:
+      abort();
+      break;
   }
   return now_tv;
 }
@@ -79,7 +87,7 @@
 void gpr_sleep_until(gpr_timespec until) {
   gpr_timespec now;
   gpr_timespec delta;
-  DWORD sleep_millis;
+  int64_t sleep_millis;
 
   for (;;) {
     /* We could simplify by using clock_nanosleep instead, but it might be
@@ -91,9 +99,10 @@
 
     delta = gpr_time_sub(until, now);
     sleep_millis =
-        (DWORD)delta.tv_sec * GPR_MS_PER_SEC + delta.tv_nsec / GPR_NS_PER_MS;
+        delta.tv_sec * GPR_MS_PER_SEC + delta.tv_nsec / GPR_NS_PER_MS;
+    GPR_ASSERT((sleep_millis >= 0) && (sleep_millis <= INT_MAX));
     GRPC_SCHEDULING_START_BLOCKING_REGION;
-    Sleep(sleep_millis);
+    Sleep((DWORD)sleep_millis);
     GRPC_SCHEDULING_END_BLOCKING_REGION;
   }
 }