diff --git a/foreign_cc/built_tools/make_build.bzl b/foreign_cc/built_tools/make_build.bzl
--- a/foreign_cc/built_tools/make_build.bzl
+++ b/foreign_cc/built_tools/make_build.bzl
@@ -35,6 +35,9 @@
             build_str += " gcc"
             dist_dir = "GccRel"
         else:
+            # Modern MSVC provides stdint.h, including the intmax_t types that
+            # Make's legacy Windows config otherwise replaces with macros.
+            build_str = 'export CL="$${CL:-}$$ /DHAVE_STDINT_H=1"\n' + build_str
             dist_dir = "WinRel"
 
         script = [