diff --git a/raster/r.mapcalc/map.c b/raster/r.mapcalc/map.c
index 36984616cc0..25b75b2bcea 100644
--- a/raster/r.mapcalc/map.c
+++ b/raster/r.mapcalc/map.c
@@ -75,7 +75,9 @@ struct map
 static struct map *maps;
 static int num_maps;
 static int max_maps;
+#ifdef HAVE_PTHREAD_H
 static int masking;
+#endif
 
 static int min_row = INT_MAX;
 static int max_row = -INT_MAX;