diff --git a/icu4c/source/common/uniset_props.cpp b/icu4c/source/common/uniset_props.cpp
index dd3f755b43e..39c3289fbb5 100644
--- a/icu4c/source/common/uniset_props.cpp
+++ b/icu4c/source/common/uniset_props.cpp
@@ -1468,6 +1468,8 @@ void UnicodeSet::applyPropertyPattern(RuleCharacterIterator& chars,
 // Inclusions list
 //----------------------------------------------------------------
 
+U_CDECL_BEGIN
+
 // USetAdder implementation
 // Does not use uset.h to reduce code dependencies
 static void U_CALLCONV
@@ -1485,6 +1487,8 @@ _set_addString(USet *set, const UChar *str, int32_t length) {
     ((UnicodeSet *)set)->add(UnicodeString((UBool)(length<0), str, length));
 }
 
+U_CDECL_END
+
 const UnicodeSet* UnicodeSet::getInclusions(UErrorCode &status) {
     umtx_lock(NULL);
     UBool f = (INCLUSIONS == NULL);
diff --git a/icu4c/source/i18n/name2uni.cpp b/icu4c/source/i18n/name2uni.cpp
index 1e5c93d2297..255a4bc63e6 100644
--- a/icu4c/source/i18n/name2uni.cpp
+++ b/icu4c/source/i18n/name2uni.cpp
@@ -29,6 +29,8 @@ static const UChar OPEN_DELIM  = 92;  // '\\' first char of OPEN
 static const UChar CLOSE_DELIM = 125; // '}'
 static const UChar SPACE       = 32;  // ' '
 
+U_CDECL_BEGIN
+
 // USetAdder implementation
 // Does not use uset.h to reduce code dependencies
 static void U_CALLCONV
@@ -46,6 +48,8 @@ _set_addString(USet *set, const UChar *str, int32_t length) {
     ((UnicodeSet *)set)->add(UnicodeString((UBool)(length<0), str, length));
 }
 
+U_CDECL_END
+
 /**
  * Constructs a transliterator with the default delimiters '{' and
  * '}'.
diff --git a/icu4c/source/test/intltest/tstnorm.cpp b/icu4c/source/test/intltest/tstnorm.cpp
index cf67769cb11..af41dfc14aa 100644
--- a/icu4c/source/test/intltest/tstnorm.cpp
+++ b/icu4c/source/test/intltest/tstnorm.cpp
@@ -1671,6 +1671,8 @@ initExpectedSkippables(UnicodeSet skipSets[UNORM_MODE_COUNT]) {
         "D6A8-\\U0001D7C9\\U0001D7CE-\\U0001D7FF\\U0002F800-\\U0002FA1D]", ""), errorCode);
 }
 
+U_CDECL_BEGIN
+
 // USetAdder implementation
 // Does not use uset.h to reduce code dependencies
 static void U_CALLCONV
@@ -1688,6 +1690,8 @@ _set_addString(USet *set, const UChar *str, int32_t length) {
     ((UnicodeSet *)set)->add(UnicodeString((UBool)(length<0), str, length));
 }
 
+U_CDECL_END
+
 void
 BasicNormalizerTest::TestSkippable() {
     UnicodeSet starts, diff, skipSets[UNORM_MODE_COUNT], expectSets[UNORM_MODE_COUNT];