diff --git a/inertia.c b/inertia.c
index 2f1fd5d..a158363 100644
--- a/inertia.c
+++ b/inertia.c
@@ -304,6 +304,7 @@ static int find_gem_candidates(int w, int h, char *grid,
     /*
      * Find the starting square.
      */
+    sx = -1;			       /* placate optimiser */
     for (sy = 0; sy < h; sy++) {
 	for (sx = 0; sx < w; sx++)
 	    if (AT(w, h, grid, sx, sy) == START)