diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,10 @@
 # ChangeLog for unix-time
 
+## v0.4.17
+
+* Fix MinGW64 linker error
+  [#67](https://github.com/kazu-yamamoto/unix-time/pull/67)
+
 ## v0.4.16
 
 * Make `tzset` optional.
diff --git a/cbits/win_patch.h b/cbits/win_patch.h
--- a/cbits/win_patch.h
+++ b/cbits/win_patch.h
@@ -118,8 +118,10 @@
 
 #if HAVE__ISBLANK_L
 #define isblank_l _isblank_l
+#ifndef _isblank_l
 // Needed to avoid -Wimplicit-function-declaration warnings
 int _isblank_l(int c, _locale_t  loc);
+#endif
 #else
 int isblank_l( int c, _locale_t _loc);
 #endif
diff --git a/unix-time.cabal b/unix-time.cabal
--- a/unix-time.cabal
+++ b/unix-time.cabal
@@ -1,6 +1,6 @@
 cabal-version:      1.18
 name:               unix-time
-version:            0.4.16
+version:            0.4.17
 license:            BSD3
 license-file:       LICENSE
 maintainer:         Kazu Yamamoto <kazu@iij.ad.jp>