diff --git a/aequilibrae/paths/results/assignment_results.py b/aequilibrae/paths/results/assignment_results.py
index d1ad3b8ab..cb2140754 100644
--- a/aequilibrae/paths/results/assignment_results.py
+++ b/aequilibrae/paths/results/assignment_results.py
@@ -79,6 +79,9 @@ def prepare(self, graph: Graph, matrix: AequilibraeMatrix) -> None:
         if graph is None:
             raise ("Please provide a graph")
         else:
+            if not graph.cost_field:
+                raise Exception('Cost field needs to be set for computation. use graph.set_graph("your_cost_field")')
+
             self.nodes = graph.num_nodes
             self.zones = graph.num_zones
             self.centroids = graph.centroids
diff --git a/aequilibrae/paths/results/path_results.py b/aequilibrae/paths/results/path_results.py
index dd0300a89..a76c86574 100644
--- a/aequilibrae/paths/results/path_results.py
+++ b/aequilibrae/paths/results/path_results.py
@@ -77,6 +77,10 @@ def prepare(self, graph: Graph) -> None:
         Args:
             *graph* (:obj:`Graph`): Needs to have been set with number of centroids and list of skims (if any)
         """
+
+        if not graph.cost_field:
+            raise Exception('Cost field needs to be set for cost computation. use graph.set_graph("your_cost_field")')
+
         self.__integer_type = graph.default_types("int")
         self.__float_type = graph.default_types("float")
         self.nodes = graph.num_nodes + 1
diff --git a/aequilibrae/paths/results/skim_results.py b/aequilibrae/paths/results/skim_results.py
index e435ca92b..df425ba4f 100644
--- a/aequilibrae/paths/results/skim_results.py
+++ b/aequilibrae/paths/results/skim_results.py
@@ -55,6 +55,9 @@ def prepare(self, graph):
             *graph* (:obj:`Graph`): Needs to have been set with number of centroids and list of skims (if any)
         """
 
+        if not graph.cost_field:
+            raise Exception('Cost field needs to be set for computation. use graph.set_graph("your_cost_field")')
+
         self.nodes = graph.num_nodes + 1
         self.zones = graph.num_zones
         self.links = graph.num_links + 1