diff --git a/format.cc b/format.cc
index 5f07c548..b04045d2 100644
--- a/format.cc
+++ b/format.cc
@@ -37,6 +37,10 @@
 
 using std::size_t;
 
+#if _MSC_VER
+# define snprintf _snprintf
+#endif
+
 namespace {
 
 // Flags.