diff --git a/src/darkleaf/di/core.clj b/src/darkleaf/di/core.clj
index df2c317e..74a5c718 100644
--- a/src/darkleaf/di/core.clj
+++ b/src/darkleaf/di/core.clj
@@ -601,12 +601,19 @@
 (defn- stop-fn [variable]
   (-> variable meta (::stop (fn no-op [_]))))
 
+(defn- validate-obj! [obj variable]
+  (when (nil? obj)
+    (throw (ex-info "A component fn must not return nil"
+                    {:type     ::nil-return
+                     :variable variable}))))
+
 (defn- var->0-component [variable]
   (let [stop (stop-fn variable)]
     (reify p/Factory
       (dependencies [_])
       (build [_ _]
-        (variable))
+        (doto (variable)
+          (validate-obj! variable)))
       (demolish [_ obj]
         (stop obj)))))
 
@@ -617,7 +624,8 @@
       (dependencies [_]
         deps)
       (build [_ deps]
-        (variable deps))
+        (doto (variable deps)
+          (validate-obj! variable)))
       (demolish [_ obj]
         (stop obj)))))
 
@@ -650,8 +658,9 @@
                      [0] (var->0-component variable)
                      [1] (var->1-component variable)
                      (throw (ex-info
-                             "The component must only have 0 or 1 arity"
-                             {:variable variable
+                             "A component fn must only have 0 or 1 arity"
+                             {:type     ::invalid-arity
+                              :variable variable
                               :arities  arities})))
         #_service  (case arities
                      [0] (var->0-service variable)
diff --git a/test/darkleaf/di/component_test.clj b/test/darkleaf/di/component_test.clj
new file mode 100644
index 00000000..9049661e
--- /dev/null
+++ b/test/darkleaf/di/component_test.clj
@@ -0,0 +1,33 @@
+(ns darkleaf.di.component-test
+  (:require
+   [clojure.test :as t]
+   [darkleaf.di.core :as di]
+   [darkleaf.di.test-utils :refer [catch-some]]))
+
+(defn nil-component-0-arity
+  {::di/kind :component}
+  []
+  nil)
+
+(defn nil-component-1-arity
+  {::di/kind :component}
+  [-deps]
+  nil)
+
+(t/deftest nil-component-0-arity-test
+  (let [ex (catch-some (di/start `nil-component-0-arity))]
+    (t/is (= ::di/nil-return (-> ex ex-cause ex-data :type)))))
+
+(t/deftest nil-component-1-arity-test
+  (let [ex (catch-some (di/start `nil-component-1-arity))]
+    (t/is (= ::di/nil-return (-> ex ex-cause ex-data :type)))))
+
+
+(defn component-2-arity
+  {::di/kind :component}
+  [deps extra-arg]
+  :smth)
+
+(t/deftest component-2-arity-test
+  (let [ex (catch-some (di/start `component-2-arity))]
+    (t/is (= ::di/invalid-arity (-> ex ex-data :type)))))