diff --git a/src/stage1/os.cpp b/src/stage1/os.cpp
index 89a9dcc944..776d2a2915 100644
--- a/src/stage1/os.cpp
+++ b/src/stage1/os.cpp
@@ -41,6 +41,7 @@
 #include <io.h>
 #include <fcntl.h>
 #include <ntsecapi.h>
+#include <math.h>
 
 // Workaround an upstream LLVM issue.
 // See https://github.com/ziglang/zig/issues/7614#issuecomment-752939981