diff --git a/dbus_service.cc b/dbus_service.cc
index 1bde41c..16b10d4 100644
--- a/dbus_service.cc
+++ b/dbus_service.cc
@@ -170,10 +170,10 @@
   }
 
   LOG(INFO) << "Setting destination channel to: " << in_target_channel;
+  string error_message;
   if (!system_state_->request_params()->SetTargetChannel(
-          in_target_channel, in_is_powerwash_allowed)) {
-    // TODO(dgarrett): Give a more specific error code/reason.
-    LogAndSetError(error, FROM_HERE, "Setting channel failed.");
+          in_target_channel, in_is_powerwash_allowed, &error_message)) {
+    LogAndSetError(error, FROM_HERE, error_message);
     return false;
   }
   return true;
diff --git a/dbus_service_unittest.cc b/dbus_service_unittest.cc
index 4ea7eec..db63b2d 100644
--- a/dbus_service_unittest.cc
+++ b/dbus_service_unittest.cc
@@ -80,7 +80,7 @@
   EXPECT_CALL(*mock_update_attempter_, RefreshDevicePolicy());
   // If SetTargetChannel is called it means the policy check passed.
   EXPECT_CALL(*fake_system_state_.mock_request_params(),
-              SetTargetChannel("stable-channel", true))
+              SetTargetChannel("stable-channel", true, _))
       .WillOnce(Return(true));
   EXPECT_TRUE(dbus_service_.SetChannel(&error_, "stable-channel", true));
   ASSERT_EQ(nullptr, error_);
@@ -93,7 +93,7 @@
   EXPECT_CALL(mock_device_policy, GetReleaseChannelDelegated(_))
       .WillOnce(DoAll(SetArgumentPointee<0>(true), Return(true)));
   EXPECT_CALL(*fake_system_state_.mock_request_params(),
-              SetTargetChannel("beta-channel", true))
+              SetTargetChannel("beta-channel", true, _))
       .WillOnce(Return(true));
 
   EXPECT_TRUE(dbus_service_.SetChannel(&error_, "beta-channel", true));
@@ -105,7 +105,7 @@
 TEST_F(UpdateEngineServiceTest, SetChannelWithInvalidChannel) {
   EXPECT_CALL(*mock_update_attempter_, RefreshDevicePolicy());
   EXPECT_CALL(*fake_system_state_.mock_request_params(),
-              SetTargetChannel("foo-channel", true)).WillOnce(Return(false));
+              SetTargetChannel("foo-channel", true, _)).WillOnce(Return(false));
 
   EXPECT_FALSE(dbus_service_.SetChannel(&error_, "foo-channel", true));
   ASSERT_NE(nullptr, error_);
diff --git a/mock_omaha_request_params.h b/mock_omaha_request_params.h
index 38d370c..5d5d47b 100644
--- a/mock_omaha_request_params.h
+++ b/mock_omaha_request_params.h
@@ -38,7 +38,7 @@
     ON_CALL(*this, GetAppId())
         .WillByDefault(testing::Invoke(
             this, &MockOmahaRequestParams::FakeGetAppId));
-    ON_CALL(*this, SetTargetChannel(testing::_, testing::_))
+    ON_CALL(*this, SetTargetChannel(testing::_, testing::_, testing::_))
         .WillByDefault(testing::Invoke(
             this, &MockOmahaRequestParams::FakeSetTargetChannel));
     ON_CALL(*this, UpdateDownloadChannel())
@@ -51,8 +51,9 @@
 
   MOCK_CONST_METHOD0(to_more_stable_channel, bool(void));
   MOCK_CONST_METHOD0(GetAppId, std::string(void));
-  MOCK_METHOD2(SetTargetChannel, bool(const std::string& channel,
-                                      bool is_powerwash_allowed));
+  MOCK_METHOD3(SetTargetChannel, bool(const std::string& channel,
+                                      bool is_powerwash_allowed,
+                                      std::string* error));
   MOCK_METHOD0(UpdateDownloadChannel, void(void));
   MOCK_CONST_METHOD0(is_powerwash_allowed, bool(void));
   MOCK_CONST_METHOD0(IsUpdateUrlOfficial, bool(void));
@@ -69,8 +70,11 @@
   }
 
   bool FakeSetTargetChannel(const std::string& channel,
-                            bool is_powerwash_allowed) {
-    return OmahaRequestParams::SetTargetChannel(channel, is_powerwash_allowed);
+                            bool is_powerwash_allowed,
+                            std::string* error) {
+    return OmahaRequestParams::SetTargetChannel(channel,
+                                                is_powerwash_allowed,
+                                                error);
   }
 
   void FakeUpdateDownloadChannel() {
diff --git a/omaha_request_params.cc b/omaha_request_params.cc
index f6fad1c..ef137b4 100644
--- a/omaha_request_params.cc
+++ b/omaha_request_params.cc
@@ -26,7 +26,9 @@
 
 #include <base/files/file_util.h>
 #include <base/strings/string_util.h>
+#include <base/strings/stringprintf.h>
 #include <brillo/key_value_store.h>
+#include <brillo/strings/string_utils.h>
 #include <policy/device_policy.h>
 
 #include "update_engine/constants.h"
@@ -131,7 +133,8 @@
 }
 
 bool OmahaRequestParams::SetTargetChannel(const string& new_target_channel,
-                                          bool is_powerwash_allowed) {
+                                          bool is_powerwash_allowed,
+                                          string* error_message) {
   LOG(INFO) << "SetTargetChannel called with " << new_target_channel
             << ", Is Powerwash Allowed = "
             << utils::ToString(is_powerwash_allowed)
@@ -139,13 +142,28 @@
             << ", existing target channel = "
             << mutable_image_props_.target_channel
             << ", download channel = " << download_channel_;
-  TEST_AND_RETURN_FALSE(IsValidChannel(new_target_channel));
+  if (!IsValidChannel(new_target_channel)) {
+    string valid_channels = brillo::string_utils::JoinRange(
+        ", ",
+        std::begin(kChannelsByStability),
+        std::end(kChannelsByStability));
+    if (error_message) {
+      *error_message = base::StringPrintf(
+          "Invalid channel name \"%s\", valid names are: %s",
+          new_target_channel.c_str(), valid_channels.c_str());
+    }
+    return false;
+  }
 
   MutableImageProperties new_props;
   new_props.target_channel = new_target_channel;
   new_props.is_powerwash_allowed = is_powerwash_allowed;
 
-  TEST_AND_RETURN_FALSE(StoreMutableImageProperties(system_state_, new_props));
+  if (!StoreMutableImageProperties(system_state_, new_props)) {
+    if (error_message)
+      *error_message = "Error storing the new channel value.";
+    return false;
+  }
   mutable_image_props_ = new_props;
   return true;
 }
diff --git a/omaha_request_params.h b/omaha_request_params.h
index b6b6f04..90cbc6e 100644
--- a/omaha_request_params.h
+++ b/omaha_request_params.h
@@ -206,7 +206,8 @@
   // numerous edge cases around ensuring the powerwash happens as intended in
   // all such cases.
   virtual bool SetTargetChannel(const std::string& channel,
-                                bool is_powerwash_allowed);
+                                bool is_powerwash_allowed,
+                                std::string* error_message);
 
   // Updates the download channel for this particular attempt from the current
   // value of target channel.  This method takes a "snapshot" of the current
diff --git a/omaha_request_params_unittest.cc b/omaha_request_params_unittest.cc
index 473b101..7ee8d98 100644
--- a/omaha_request_params_unittest.cc
+++ b/omaha_request_params_unittest.cc
@@ -353,7 +353,7 @@
     OmahaRequestParams params(&fake_system_state_);
     params.set_root(test_dir_);
     EXPECT_TRUE(params.Init("", "", false));
-    params.SetTargetChannel("canary-channel", false);
+    params.SetTargetChannel("canary-channel", false, nullptr);
     EXPECT_FALSE(params.is_powerwash_allowed());
   }
   OmahaRequestParams out(&fake_system_state_);
@@ -375,7 +375,7 @@
     OmahaRequestParams params(&fake_system_state_);
     params.set_root(test_dir_);
     EXPECT_TRUE(params.Init("", "", false));
-    params.SetTargetChannel("canary-channel", true);
+    params.SetTargetChannel("canary-channel", true, nullptr);
     EXPECT_TRUE(params.is_powerwash_allowed());
   }
   OmahaRequestParams out(&fake_system_state_);
@@ -398,7 +398,11 @@
     params.set_root(test_dir_);
     SetLockDown(true);
     EXPECT_TRUE(params.Init("", "", false));
-    params.SetTargetChannel("dogfood-channel", true);
+    string error_message;
+    EXPECT_FALSE(
+        params.SetTargetChannel("dogfood-channel", true, &error_message));
+    // The error message should include a message about the valid channels.
+    EXPECT_NE(string::npos, error_message.find("stable-channel"));
     EXPECT_FALSE(params.is_powerwash_allowed());
   }
   OmahaRequestParams out(&fake_system_state_);
@@ -459,23 +463,23 @@
   // When an invalid value is set, it should be ignored and the
   // value from lsb-release should be used instead.
   params_.Init("", "", false);
-  EXPECT_FALSE(params_.SetTargetChannel("invalid-channel", false));
+  EXPECT_FALSE(params_.SetTargetChannel("invalid-channel", false, nullptr));
   EXPECT_EQ("dev-channel", params_.target_channel());
 
   // When set to a valid value, it should take effect.
   params_.Init("", "", false);
-  EXPECT_TRUE(params_.SetTargetChannel("beta-channel", true));
+  EXPECT_TRUE(params_.SetTargetChannel("beta-channel", true, nullptr));
   EXPECT_EQ("beta-channel", params_.target_channel());
 
   // When set to the same value, it should be idempotent.
   params_.Init("", "", false);
-  EXPECT_TRUE(params_.SetTargetChannel("beta-channel", true));
+  EXPECT_TRUE(params_.SetTargetChannel("beta-channel", true, nullptr));
   EXPECT_EQ("beta-channel", params_.target_channel());
 
   // When set to a valid value while a change is already pending, it should
   // succeed.
   params_.Init("", "", false);
-  EXPECT_TRUE(params_.SetTargetChannel("stable-channel", true));
+  EXPECT_TRUE(params_.SetTargetChannel("stable-channel", true, nullptr));
   EXPECT_EQ("stable-channel", params_.target_channel());
 
   // Set a different channel in stateful LSB release.
@@ -487,7 +491,7 @@
   // When set to a valid value while a change is already pending, it should
   // succeed.
   params_.Init("", "", false);
-  EXPECT_TRUE(params_.SetTargetChannel("beta-channel", true));
+  EXPECT_TRUE(params_.SetTargetChannel("beta-channel", true, nullptr));
   // The target channel should reflect the change, but the download channel
   // should continue to retain the old value ...
   EXPECT_EQ("beta-channel", params_.target_channel());
diff --git a/omaha_response_handler_action_unittest.cc b/omaha_response_handler_action_unittest.cc
index 5e62f45..eb6a5af 100644
--- a/omaha_response_handler_action_unittest.cc
+++ b/omaha_response_handler_action_unittest.cc
@@ -387,7 +387,7 @@
   params.set_root(test_dir);
   params.Init("5.6.7.8", "", 0);
   EXPECT_EQ("stable-channel", params.current_channel());
-  params.SetTargetChannel("canary-channel", false);
+  params.SetTargetChannel("canary-channel", false, nullptr);
   EXPECT_EQ("canary-channel", params.target_channel());
   EXPECT_FALSE(params.to_more_stable_channel());
   EXPECT_FALSE(params.is_powerwash_allowed());
diff --git a/update_attempter.cc b/update_attempter.cc
index 09dd108..7d6aaf2 100644
--- a/update_attempter.cc
+++ b/update_attempter.cc
@@ -381,7 +381,11 @@
     LOG(INFO) << "Setting target channel as mandated: " << target_channel;
     // Pass in false for powerwash_allowed until we add it to the policy
     // protobuf.
-    omaha_request_params_->SetTargetChannel(target_channel, false);
+    string error_message;
+    if (!omaha_request_params_->SetTargetChannel(target_channel, false,
+                                                 &error_message)) {
+      LOG(ERROR) << "Setting the channel failed: " << error_message;
+    }
 
     // Since this is the beginning of a new attempt, update the download
     // channel. The download channel won't be updated until the next attempt,