diff --git a/src/stage1/os.cpp b/src/stage1/os.cpp
index 5e5e08b0836de8ebb5e8b832c8a2dc80552d405a..49544102b2bbcc8b7b162b4e815d4dda4d28d3c3 100644
--- a/src/stage1/os.cpp
+++ b/src/stage1/os.cpp
@@ -42,7 +42,9 @@
 #include <fcntl.h>
 #include <ntsecapi.h>
 
-#if defined(_MSC_VER)
+// Workaround an upstream LLVM issue.
+// See https://github.com/ziglang/zig/issues/7614#issuecomment-752939981
+#if defined(_MSC_VER) && defined(_WIN64)
 typedef SSIZE_T ssize_t;
 #endif
 #else