diff --git a/update_manager/update_manager-inl.h b/update_manager/update_manager-inl.h
index 1b1dc49..544a371 100644
--- a/update_manager/update_manager-inl.h
+++ b/update_manager/update_manager-inl.h
@@ -28,13 +28,13 @@
                                                       result, args...);
 
   if (status == EvalStatus::kFailed) {
-    LOG(WARNING) << "PolicyRequest() failed with error: " << error;
+    LOG(WARNING) << "Policy request failed: " << error;
     error.clear();
     status = (default_policy_.*policy_method)(ec, state_.get(), &error,
                                               result, args...);
 
     if (status == EvalStatus::kFailed) {
-      LOG(WARNING) << "Request to DefaultPolicy also failed, passing error.";
+      LOG(WARNING) << "Request to default policy also failed: " << error;
     }
   }
   // TODO(deymo): Log the actual state used from the EvaluationContext.
@@ -86,7 +86,13 @@
   // IMPORTANT: To ensure that ActualArgs can be converted to ExpectedArgs, we
   // explicitly instantiate EvaluatePolicy with the latter in lieu of the
   // former.
-  return EvaluatePolicy<R, ExpectedArgs...>(ec, policy_method, result, args...);
+  EvalStatus ret = EvaluatePolicy<R, ExpectedArgs...>(ec, policy_method, result,
+                                                      args...);
+  // Sync policy requests must not block, if they do then this is an error.
+  DCHECK(EvalStatus::kAskMeAgainLater != ret);
+  LOG_IF(WARNING, EvalStatus::kAskMeAgainLater == ret)
+      << "Sync request used with an async policy";
+  return ret;
 }
 
 template<typename R, typename... ActualArgs, typename... ExpectedArgs>
diff --git a/update_manager/update_manager.h b/update_manager/update_manager.h
index b3dfc7f..8c96d7b 100644
--- a/update_manager/update_manager.h
+++ b/update_manager/update_manager.h
@@ -34,11 +34,10 @@
   // |policy_method|.
   //
   // When the policy request succeeds, the |result| is set and the method
-  // returns EvalStatus::kSucceeded, otherwise, the |result| may not be set.
-  // Also, if the policy implementation should block, this method returns
-  // immediately with EvalStatus::kAskMeAgainLater. In case of failure
-  // EvalStatus::kFailed is returned and the |error| message is set, which must
-  // not be NULL.
+  // returns EvalStatus::kSucceeded, otherwise, the |result| may not be set.  A
+  // policy called with this method should not block (i.e. return
+  // EvalStatus::kAskMeAgainLater), which is considered a programming error. On
+  // failure, EvalStatus::kFailed is returned.
   //
   // An example call to this method is:
   //   um.PolicyRequest(&Policy::SomePolicyMethod, &bool_result, arg1, arg2);
@@ -77,7 +76,7 @@
  private:
   FRIEND_TEST(UmUpdateManagerTest, PolicyRequestCallsPolicy);
   FRIEND_TEST(UmUpdateManagerTest, PolicyRequestCallsDefaultOnError);
-  FRIEND_TEST(UmUpdateManagerTest, PolicyRequestDoesntBlock);
+  FRIEND_TEST(UmUpdateManagerTest, PolicyRequestDoesntBlockDeathTest);
   FRIEND_TEST(UmUpdateManagerTest, AsyncPolicyRequestDelaysEvaluation);
 
   // EvaluatePolicy() evaluates the passed |policy_method| method on the current
diff --git a/update_manager/update_manager_unittest.cc b/update_manager/update_manager_unittest.cc
index 39427b3..95fd3e0 100644
--- a/update_manager/update_manager_unittest.cc
+++ b/update_manager/update_manager_unittest.cc
@@ -128,14 +128,16 @@
   EXPECT_TRUE(result.updates_enabled);
 }
 
-TEST_F(UmUpdateManagerTest, PolicyRequestDoesntBlock) {
+// This test only applies to debug builds where DCHECK is enabled.
+#if DCHECK_IS_ON
+TEST_F(UmUpdateManagerTest, PolicyRequestDoesntBlockDeathTest) {
+  // The update manager should die (DCHECK) if a policy called synchronously
+  // returns a kAskMeAgainLater value.
   UpdateCheckParams result;
   umut_->set_policy(new LazyPolicy());
-
-  EvalStatus status = umut_->PolicyRequest(
-      &Policy::UpdateCheckAllowed, &result);
-  EXPECT_EQ(EvalStatus::kAskMeAgainLater, status);
+  EXPECT_DEATH(umut_->PolicyRequest(&Policy::UpdateCheckAllowed, &result), "");
 }
+#endif  // DCHECK_IS_ON
 
 TEST_F(UmUpdateManagerTest, AsyncPolicyRequestDelaysEvaluation) {
   // To avoid differences in code execution order between an AsyncPolicyRequest