diff --git a/raster/r.viewshed/viewshed.cpp b/raster/r.viewshed/viewshed.cpp
index 94bd1d566e4..3ce07fa4652 100644
--- a/raster/r.viewshed/viewshed.cpp
+++ b/raster/r.viewshed/viewshed.cpp
@@ -261,7 +261,7 @@ MemoryVisibilityGrid *viewshed_in_memory(char *inputfname, GridHeader *hd,
         e.elev[0] = data[0][i];
         e.elev[1] = data[1][i];
         e.elev[2] = data[2][i];
-        e.angle = -1;
+        e.angle = -1.0;
 
         if (!is_nodata(visgrid->grid->hd, data[1][i]) &&
             !is_point_outside_max_dist(*vp, *hd, sn.row, sn.col,
@@ -500,7 +500,7 @@ IOVisibilityGrid *viewshed_external(char *inputfname, GridHeader *hd,
         e.elev[0] = data[0][i];
         e.elev[1] = data[1][i];
         e.elev[2] = data[2][i];
-        e.angle = -1;
+        e.angle = -1.0;
         if (!is_nodata(visgrid->hd, data[1][i]) &&
             !is_point_outside_max_dist(*vp, *hd, sn.row, sn.col,
                                        viewOptions.maxDist)) {