diff --git a/src/util/string_conversion.hpp b/src/util/string_conversion.hpp
index 9adb982..02e6c57 100644
--- a/src/util/string_conversion.hpp
+++ b/src/util/string_conversion.hpp
@@ -183,7 +183,7 @@ namespace gz {
     inline std::string toString(const T& t) {
         std::string s = "( ";
         s += toString(t.x) + ", ";
-        s += toString(t.z) + " )";
+        s += toString(t.y) + " )";
         return s;
     }