diff --git a/icu4c/source/common/umutex.cpp b/icu4c/source/common/umutex.cpp
index b3478ad72a..c699e34c8f 100644
--- a/icu4c/source/common/umutex.cpp
+++ b/icu4c/source/common/umutex.cpp
@@ -68,7 +68,7 @@ U_NAMESPACE_BEGIN
 U_COMMON_API UBool U_EXPORT2 umtx_initImplPreInit(UInitOnce &uio) {
     for (;;) {
         int32_t previousState = InterlockedCompareExchange(
-#if (U_PLATFORM == U_PF_MINGW) || (U_PLATFORM == U_PF_CYGWIN)
+#if (U_PLATFORM == U_PF_MINGW) || (U_PLATFORM == U_PF_CYGWIN) || defined(__clang__)
            (LONG volatile *) // this is the type given in the API doc for this function.
 #endif
             &uio.fState,  //  Destination