diff --git a/osm/osm_types.py b/osm/osm_types.py
index a8ad076..399abba 100644
--- a/osm/osm_types.py
+++ b/osm/osm_types.py
@@ -9,7 +9,7 @@ class OSMWay:
     highway: str = field(init=False, default="")
     area: Optional[str] = field(init=False, default=None)
     max_speed_str: Optional[str] = field(init=False, default=None)
-    max_speed_int: int = field(init=False)
+    max_speed_int: int = field(init=False, default=0)
     direction: str = field(init=False, default="")
     forward: bool = field(init=False, default=True)
     backward: bool = field(init=False, default=True)
diff --git a/tests/convert_graph_test.py b/tests/convert_graph_test.py
index d12c88c..6ab204a 100644
--- a/tests/convert_graph_test.py
+++ b/tests/convert_graph_test.py
@@ -1,3 +1,4 @@
+import importlib.util
 import random
 import string
 import unittest
@@ -6,6 +7,8 @@
 from graph.graph import Graph
 from graph.graph_types import Edge, EdgeData, Vertex, VertexData
 
+networkx_available = importlib.util.find_spec("networkx") is not None
+
 
 def random_string(length=8):
     return "".join(random.choice(string.ascii_lowercase) for i in range(length))
@@ -15,6 +18,7 @@ def random_uint(max_val=1000):
     return random.randint(1, max_val)
 
 
+@unittest.skipUnless(networkx_available, "networkx is an optional dependency and is not installed")
 class TestConvertGraphTest(unittest.TestCase):
     def test_converting_K4_graph(self):
         g = self.create_graph(number_nodes=4)
diff --git a/tests/integration_test.py b/tests/integration_test.py
index 36152e5..e06b559 100644
--- a/tests/integration_test.py
+++ b/tests/integration_test.py
@@ -1,6 +1,9 @@
+import importlib.util
 import unittest
 from subprocess import call
 
+networkx_available = importlib.util.find_spec("networkx") is not None
+
 
 class IntegrationTest(unittest.TestCase):
     def test_python(self):
@@ -21,18 +24,12 @@ def pedestrian_graph_contracted_ok(self):
         self.assertEqual(nmb_edges, 2039)
 
     def _execute_program(self):
-        returncode = call(
-            [
-                "python3",
-                "run.py",
-                "-f",
-                "data/karlsruhe_small.osm",
-                "-n",
-                "p",
-                "-c",
-                "--networkx",
-            ]
-        )
+        args = ["python3", "run.py", "-f", "data/karlsruhe_small.osm", "-n", "p", "-c"]
+        # --networkx requires the optional networkx dependency; only exercise
+        # it when networkx is actually installed
+        if networkx_available:
+            args.append("--networkx")
+        returncode = call(args)
         self.assertEqual(0, returncode)
 
     def _get_nmb_nodes_edges(self, path):