diff --git a/example/voronoi_basic_tutorial.cpp b/example/voronoi_basic_tutorial.cpp
index ea2b9e6..bf1c303 100644
--- a/example/voronoi_basic_tutorial.cpp
+++ b/example/voronoi_basic_tutorial.cpp
@@ -167,7 +167,7 @@ int main() {
       if (it->contains_point()) {
         std::size_t index = it->source_index();
         Point p = points[index];
-        printf("Cell #%ud contains a point: (%d, %d).\n",
+        printf("Cell #%u contains a point: (%d, %d).\n",
                cell_index, x(p), y(p));
       } else {
         std::size_t index = it->source_index() - points.size();
@@ -175,14 +175,14 @@ int main() {
         Point p1 = high(segments[index]);
         if (it->source_category() ==
             boost::polygon::SOURCE_CATEGORY_SEGMENT_START_POINT) {
-          printf("Cell #%ud contains segment start point: (%d, %d).\n",
+          printf("Cell #%u contains segment start point: (%d, %d).\n",
                  cell_index, x(p0), y(p0));
         } else if (it->source_category() ==
                    boost::polygon::SOURCE_CATEGORY_SEGMENT_END_POINT) {
-          printf("Cell #%ud contains segment end point: (%d, %d).\n",
+          printf("Cell #%u contains segment end point: (%d, %d).\n",
                  cell_index, x(p0), y(p0));
         } else {
-          printf("Cell #%ud contains a segment: ((%d, %d), (%d, %d)). \n",
+          printf("Cell #%u contains a segment: ((%d, %d), (%d, %d)). \n",
                  cell_index, x(p0), y(p0), x(p1), y(p1));
         }
       }