diff --git a/test/unit/vertex_adapter/vertex_adapter.cpp b/test/unit/vertex_adapter/vertex_adapter.cpp
index 4c79e6bb3..269b09106 100644
--- a/test/unit/vertex_adapter/vertex_adapter.cpp
+++ b/test/unit/vertex_adapter/vertex_adapter.cpp
@@ -273,7 +273,7 @@ SECTION("polygon with empty exterior ring") {
     g.emplace_back();
 
     mapnik::geometry::polygon_vertex_adapter<double> va(g);
-    double x,y;
+    double x = 0, y = 0;
     unsigned cmd;
 
     cmd = va.vertex(&x,&y);