diff --git a/unittest/error-interface-field.yaml b/unittest/error-schema-field1.yaml
similarity index 100%
rename from unittest/error-interface-field.yaml
rename to unittest/error-schema-field1.yaml
diff --git a/unittest/error-schema-field2.yaml b/unittest/error-schema-field2.yaml
new file mode 100644
index 0000000..13fb41d
--- /dev/null
+++ b/unittest/error-schema-field2.yaml
@@ -0,0 +1,18 @@
+test:
+  description: "A bunch of schema fields with the wrong type"
+  errors:
+    expected:
+     - "yamale: .* is not a "
+    count: 9
+---
+interfaces:
+  GigabitEthernet1/0/0:
+    description: 1234
+    lcp: True
+    mac: "0001.0203.0405"
+    addresses: [ 1234, "hello world", 192.0.2.1, 2001:db8::1 ]
+    sub-interfaces:
+      100:
+        description: [ "a", "list" ]
+        encapsulation:
+          dot1q: "hello world"
diff --git a/validator/__init__.py b/validator/__init__.py
index 4d741b6..e342764 100644
--- a/validator/__init__.py
+++ b/validator/__init__.py
@@ -33,6 +33,8 @@ class IPInterfaceWithPrefixLength(Validator):
             network = ipaddress.ip_interface(value)
         except:
             return False
+        if not isinstance(value, str):
+            return False
         if not '/' in value:
             return False
         e = value.split('/')