diff --git a/dlls/wined3d/shader.c b/dlls/wined3d/shader.c
index caba7db..35f5cf2 100644
--- a/dlls/wined3d/shader.c
+++ b/dlls/wined3d/shader.c
@@ -275,12 +275,14 @@ int shader_vaddline(struct wined3d_string_buffer *buffer, const char *format, va
     int rc;
     char *new_buffer;
     unsigned int new_buffer_size;
+    va_list cur_args;
 
     for (;;)
     {
         rem = buffer->buffer_size - buffer->content_size;
-        rc = vsnprintf(&buffer->buffer[buffer->content_size], rem, format, args);
-
+        va_copy(cur_args, args);
+        rc = vsnprintf(&buffer->buffer[buffer->content_size], rem, format, cur_args);
+        va_end(cur_args);
         if (rc >= 0 /* C89 */ && (unsigned int)rc < rem /* C99 */)
             break;