diff --git a/codemp/game/q_shared.c b/codemp/game/q_shared.c
index fd7da90..5d60f01 100644
--- a/codemp/game/q_shared.c
+++ b/codemp/game/q_shared.c
@@ -850,6 +850,39 @@ char* Q_strrchr( const char* string, int c )
 	return sp;
 }
 
+#ifdef _MSC_VER
+/*
+=============
+Q_vsnprintf
+
+Special wrapper function for Microsoft's broken _vsnprintf() function.
+MinGW comes with its own snprintf() which is not broken.
+=============
+*/
+
+int Q_vsnprintf(char *str, size_t size, const char *format, va_list ap)
+{
+	int retval;
+	
+	retval = _vsnprintf(str, size, format, ap);
+
+	if(retval < 0 || retval == size)
+	{
+		// Microsoft doesn't adhere to the C99 standard of vsnprintf,
+		// which states that the return value must be the number of
+		// bytes written if the output string had sufficient length.
+		//
+		// Obviously we cannot determine that value from Microsoft's
+		// implementation, so we have no choice but to return size.
+		
+		str[size - 1] = '\0';
+		return size;
+	}
+	
+	return retval;
+}
+#endif
+
 /*
 =============
 Q_strncpyz
diff --git a/codemp/game/q_shared.h b/codemp/game/q_shared.h
index 2730466..5264fb6 100644
--- a/codemp/game/q_shared.h
+++ b/codemp/game/q_shared.h
@@ -88,6 +88,14 @@ extern int g_G2AllocServer;
 #include <ctype.h>
 #include <limits.h>
 
+#ifdef _MSC_VER
+  // vsnprintf is ISO/IEC 9899:1999
+  // abstracting this to make it portable
+  int Q_vsnprintf(char *str, size_t size, const char *format, va_list ap);
+#else
+  #define Q_vsnprintf vsnprintf
+#endif
+
 // Special min treatment for Xbox C++ version
 
 #ifdef _XBOX