diff --git a/icu4c/source/tools/toolutil/pkg_genc.h b/icu4c/source/tools/toolutil/pkg_genc.h
index 72d96870355..310e5f144bc 100644
--- a/icu4c/source/tools/toolutil/pkg_genc.h
+++ b/icu4c/source/tools/toolutil/pkg_genc.h
@@ -52,8 +52,7 @@
 #define USE_SINGLE_CCODE_FILE
 #endif
 
-/* Need to fix the file seperator character when using MinGW. */
-#if defined(WINDOWS_WITH_GNUC) || defined(USING_CYGWIN)
+#if defined(WINDOWS_WITH_GNUC) || defined(USING_CYGWIN) || U_PLATFORM == U_PF_MINGW
 #define PKGDATA_FILE_SEP_STRING "/"
 #else
 #define PKGDATA_FILE_SEP_STRING U_FILE_SEP_STRING