diff --git a/icu4c/source/common/util.cpp b/icu4c/source/common/util.cpp
index e456047c0e8..6b74ffe5b16 100644
--- a/icu4c/source/common/util.cpp
+++ b/icu4c/source/common/util.cpp
@@ -428,14 +428,14 @@ uprv_isRuleWhiteSpace(UChar32 c) {
              c == 0x200E || c == 0x200F || c >= 0x2028));
 }
 
-U_CAPI UnicodeSet* U_EXPORT2
+U_CAPI U_NAMESPACE_QUALIFIER UnicodeSet* U_EXPORT2
 uprv_openRuleWhiteSpaceSet(UErrorCode* ec) {
     if(U_FAILURE(*ec)) {
         return NULL;
     }
     // create a set with the Pattern_White_Space characters,
     // without a pattern for fewer code dependencies
-    UnicodeSet *set=new UnicodeSet(9, 0xd);
+    U_NAMESPACE_QUALIFIER UnicodeSet *set=new U_NAMESPACE_QUALIFIER UnicodeSet(9, 0xd);
     set->UnicodeSet::add(0x20).add(0x85).add(0x200e, 0x200f).add(0x2028, 0x2029);
     return set;
 }
diff --git a/icu4c/source/common/util.h b/icu4c/source/common/util.h
index c411fce824e..37fb56868e4 100644
--- a/icu4c/source/common/util.h
+++ b/icu4c/source/common/util.h
@@ -244,7 +244,7 @@ U_NAMESPACE_END
  * See UAX #31 Identifier and Pattern Syntax: http://www.unicode.org/reports/tr31/
  * @internal
  */
-U_CAPI UnicodeSet* U_EXPORT2
+U_CAPI U_NAMESPACE_QUALIFIER UnicodeSet* U_EXPORT2
 uprv_openRuleWhiteSpaceSet(UErrorCode* ec);
 
 /**