diff --git a/icu4c/source/i18n/digitlst.cpp b/icu4c/source/i18n/digitlst.cpp
index f68f8bb3227..a3b3406ca64 100644
--- a/icu4c/source/i18n/digitlst.cpp
+++ b/icu4c/source/i18n/digitlst.cpp
@@ -26,7 +26,7 @@
 ******************************************************************************
 */
 
-#if U_PLATFORM == U_PF_CYGWIN
+#if defined(__CYGWIN__) && !defined(_GNU_SOURCE)
 #define _GNU_SOURCE
 #endif