diff --git a/condition.go b/condition.go
index 9180e39..012c869 100644
--- a/condition.go
+++ b/condition.go
@@ -55,8 +55,10 @@ func (cs Conditions) UnmarshalJSON(data []byte) error {
 	}
 
 	for k, jc := range jcs {
+		var found bool
 		for name, c := range ConditionFactories {
 			if name == jc.Type {
+				found = true
 				dc = c()
 
 				if len(jc.Options) == 0 {
@@ -72,6 +74,10 @@ func (cs Conditions) UnmarshalJSON(data []byte) error {
 				break
 			}
 		}
+
+		if !found {
+			return errors.Errorf("Could not find condition type %s", jc.Type)
+		}
 	}
 
 	return nil
diff --git a/condition_test.go b/condition_test.go
index 92fa021..389eb4f 100644
--- a/condition_test.go
+++ b/condition_test.go
@@ -54,3 +54,12 @@ func TestMarshalUnmarshal(t *testing.T) {
 	assert.IsType(t, &EqualsSubjectCondition{}, cs["owner"])
 	assert.IsType(t, &CIDRCondition{}, cs["clientIP"])
 }
+
+func TestUnmarshalFails(t *testing.T) {
+	cs := Conditions{}
+	require.NotNil(t, json.Unmarshal([]byte(`{
+	"somefield": {
+		"type": "DoesntExist"
+	}
+}`), &cs))
+}