document cell -DSPU_MAIN_PARAM_LONG_LONG flag
diff --git a/docs/cell.html b/docs/cell.html
index 4fd12e2..7104c84 100644
--- a/docs/cell.html
+++ b/docs/cell.html
@@ -37,6 +37,11 @@
 </p>
 
 <p>
+If using Cell SDK 3.0, first edit configs/linux-cell and add
+<code>-DSPU_MAIN_PARAM_LONG_LONG</code> to the SPU_CFLAGS.
+</p>
+
+<p>
 To compile the code, run <code>make linux-cell</code>.
 </p>