diff --git a/grid.c b/grid.c
index bae29f4..6a90c99 100644
--- a/grid.c
+++ b/grid.c
@@ -1069,7 +1069,7 @@ void grid_find_incentre(grid_face *f)
                     eq[2] = eqs[0][3]*eqs[1][2] - eqs[1][3]*eqs[0][2];
 
                     /* Parametrise x and y in terms of some t. */
-                    if (abs(eq[0]) < abs(eq[1])) {
+                    if (fabs(eq[0]) < fabs(eq[1])) {
                         /* Parameter is x. */
                         xt[0] = 1; xt[1] = 0;
                         yt[0] = -eq[0]/eq[1]; yt[1] = eq[2]/eq[1];
diff --git a/signpost.c b/signpost.c
index 5650b2b..9dd8699 100644
--- a/signpost.c
+++ b/signpost.c
@@ -1982,7 +1982,7 @@ static void draw_drag_indicator(drawing *dr, game_drawstate *ds,
         /* Draw an arrow pointing away from/towards the origin cell. */
         int ox = COORD(ui->sx) + TILE_SIZE/2, oy = COORD(ui->sy) + TILE_SIZE/2;
         double tana, offset;
-        double xdiff = fabs(ox - ui->dx), ydiff = fabs(oy - ui->dy);
+        double xdiff = abs(ox - ui->dx), ydiff = abs(oy - ui->dy);
 
         if (xdiff == 0) {
             ang = (oy > ui->dy) ? 0.0F : PI;