diff --git a/README.chromium b/README.chromium
index 6b5200e..921a8c5 100644
--- a/README.chromium
+++ b/README.chromium
@@ -282,5 +282,4 @@
     https://unicode-org.atlassian.net/browse/ICU-20302
   - Fix:
     https://github.com/unicode-org/icu/pull/315
-
-   
+    https://github.com/unicode-org/icu/pull/318
diff --git a/patches/win7_tz.patch b/patches/win7_tz.patch
index 4406e6b..97fae84 100644
--- a/patches/win7_tz.patch
+++ b/patches/win7_tz.patch
@@ -29,3 +29,16 @@
  
      if (U_FAILURE(status)) {
          return nullptr;
+diff --git a/source/common/wintz.h b/source/common/wintz.h
+index f98b1779..cd8565ee 100644
+--- a/source/common/wintz.h
++++ b/source/common/wintz.h
+@@ -28,7 +28,7 @@ U_CDECL_BEGIN
+ typedef struct _TIME_ZONE_INFORMATION TIME_ZONE_INFORMATION;
+ U_CDECL_END
+ 
+-U_CFUNC const char* U_EXPORT2
++U_INTERNAL const char* U_EXPORT2
+ uprv_detectWindowsTimeZone();
+ 
+ #endif /* U_PLATFORM_USES_ONLY_WIN32_API  */
diff --git a/source/common/wintz.h b/source/common/wintz.h
index f98b177..cd8565e 100644
--- a/source/common/wintz.h
+++ b/source/common/wintz.h
@@ -28,7 +28,7 @@
 typedef struct _TIME_ZONE_INFORMATION TIME_ZONE_INFORMATION;
 U_CDECL_END
 
-U_CFUNC const char* U_EXPORT2
+U_INTERNAL const char* U_EXPORT2
 uprv_detectWindowsTimeZone();
 
 #endif /* U_PLATFORM_USES_ONLY_WIN32_API  */