diff --git a/icu4c/source/i18n/unicode/regex.h b/icu4c/source/i18n/unicode/regex.h
index 95d68910d0..184c57b26b 100644
--- a/icu4c/source/i18n/unicode/regex.h
+++ b/icu4c/source/i18n/unicode/regex.h
@@ -78,6 +78,7 @@ class  RegexCImpl;
 U_INTERNAL void U_EXPORT2
     RegexPatternDump(const RegexPattern *pat);
 #else
+    #undef RegexPatternDump
     #define RegexPatternDump(pat)
 #endif