diff --git a/dicompylercore/structure.py b/dicompylercore/structure.py
index 306ed2b..9eff6c8 100644
--- a/dicompylercore/structure.py
+++ b/dicompylercore/structure.py
@@ -380,7 +380,7 @@ def show3d(self, rows=512, cols=512):
         for structure in self.structures.values():
             for loc, loccontours in structure.contours.items():
                 for contour in loccontours:
-                    data = contour["data"]
+                    data = np.array(contour["data"])
                     x = data[:, 0]
                     y = data[:, 1]
                     # Append the first point to the end
@@ -935,7 +935,7 @@ def show3d(self, rows=512, cols=512):
 
         for loc, loccontours in contours.items():
             for contour in loccontours:
-                data = contour["data"]
+                data = np.array(contour["data"])
                 x = data[:, 0]
                 y = data[:, 1]
                 # Append the first point to the end