diff --git a/flang/runtime/random.cpp b/flang/runtime/random.cpp
--- a/flang/runtime/random.cpp
+++ b/flang/runtime/random.cpp
@@ -57,7 +57,7 @@
       Int fraction{generator()};
       if constexpr (words > 1) {
         for (std::size_t k{1}; k < words; ++k) {
-          static constexpr Int rangeMask{(Int{1} << rangeBits) - 1};
+          static constexpr auto rangeMask{(GeneratedWord{1} << rangeBits) - 1};
           GeneratedWord word{(generator() - generator.min()) & rangeMask};
           fraction = (fraction << rangeBits) | word;
         }