diff --git a/src/hydra-queue-runner/builder.cc b/src/hydra-queue-runner/builder.cc
index 2a31ff2e..9fe2e45b 100644
--- a/src/hydra-queue-runner/builder.cc
+++ b/src/hydra-queue-runner/builder.cc
@@ -84,9 +84,16 @@ State::StepResult State::doBuildStep(nix::ref<Store> destStore, Step::ptr step,
             return sMaybeCancelled;
         }
 
-        for (auto build2 : dependents)
-            if (build2->drvPath == step->drvPath) { build = build2; break; }
-
+        for (auto build2 : dependents) {
+            if (build2->drvPath == step->drvPath) {
+              build = build2;
+              {
+                  auto notificationSenderQueue_(notificationSenderQueue.lock());
+                  notificationSenderQueue_->push(NotificationItem{NotificationItem::Type::Started, build->id});
+              }
+              notificationSenderWakeup.notify_one();
+            }
+        }
         if (!build) build = *dependents.begin();
 
         printMsg(lvlInfo, format("performing step ‘%1%’ on ‘%2%’ (needed by build %3% and %4% others)")
@@ -249,7 +256,7 @@ State::StepResult State::doBuildStep(nix::ref<Store> destStore, Step::ptr step,
         for (auto id : buildIDs) {
             {
                 auto notificationSenderQueue_(notificationSenderQueue.lock());
-                notificationSenderQueue_->push(NotificationItem(id, std::vector<BuildID>()));
+                notificationSenderQueue_->push(NotificationItem{NotificationItem::Type::Finished, id});
             }
             notificationSenderWakeup.notify_one();
         }
@@ -369,7 +376,7 @@ State::StepResult State::doBuildStep(nix::ref<Store> destStore, Step::ptr step,
         /* Send notification about this build and its dependents. */
         {
             auto notificationSenderQueue_(notificationSenderQueue.lock());
-            notificationSenderQueue_->push(NotificationItem(build->id, dependentIDs));
+            notificationSenderQueue_->push(NotificationItem{NotificationItem::Type::Finished, build->id, dependentIDs});
         }
         notificationSenderWakeup.notify_one();
 
diff --git a/src/hydra-queue-runner/hydra-queue-runner.cc b/src/hydra-queue-runner/hydra-queue-runner.cc
index b1842523..d0305441 100644
--- a/src/hydra-queue-runner/hydra-queue-runner.cc
+++ b/src/hydra-queue-runner/hydra-queue-runner.cc
@@ -482,11 +482,11 @@ void State::notificationSender()
                 notificationSenderQueue_->pop();
             }
 
-            printMsg(lvlChatty, format("sending notification about build %1%") % item.first);
+            printMsg(lvlChatty, format("sending notification about build %1%") % item.id);
 
             Pid pid = startProcess([&]() {
-                Strings argv({"hydra-notify", "build", std::to_string(item.first)});
-                for (auto id : item.second)
+                Strings argv({"hydra-notify", item.type == NotificationItem::Type::Started ? "build-started" : "build-finished", std::to_string(item.id)});
+                for (auto id : item.dependentIds)
                     argv.push_back(std::to_string(id));
                 execvp("hydra-notify", (char * *) stringsToCharPtrs(argv).data()); // FIXME: remove cast
                 throw SysError("cannot start hydra-notify");
@@ -496,7 +496,7 @@ void State::notificationSender()
 
             if (res != 0)
                 throw Error(format("hydra-build returned exit code %1% notifying about build %2%")
-                    % res % item.first);
+                    % res % item.id);
 
         } catch (std::exception & e) {
             printMsg(lvlError, format("notification sender: %1%") % e.what());
diff --git a/src/hydra-queue-runner/state.hh b/src/hydra-queue-runner/state.hh
index 34f6eaa1..d8e6caed 100644
--- a/src/hydra-queue-runner/state.hh
+++ b/src/hydra-queue-runner/state.hh
@@ -318,7 +318,16 @@ private:
        killed before it has finished sending notifications about a
        build, then the notifications may be lost. It would be better
        to mark builds with pending notification in the database. */
-    typedef std::pair<BuildID, std::vector<BuildID>> NotificationItem;
+    struct NotificationItem
+    {
+        enum class Type : char {
+           Started,
+           Finished
+        };
+        Type type;
+        BuildID id;
+        std::vector<BuildID> dependentIds;
+    };
     nix::Sync<std::queue<NotificationItem>> notificationSenderQueue;
     std::condition_variable notificationSenderWakeup;
 
diff --git a/src/lib/Hydra/Helper/PluginHooks.pm b/src/lib/Hydra/Helper/PluginHooks.pm
index 4000045b..2813ac65 100644
--- a/src/lib/Hydra/Helper/PluginHooks.pm
+++ b/src/lib/Hydra/Helper/PluginHooks.pm
@@ -5,8 +5,21 @@ use Exporter;
 
 our @ISA = qw(Exporter);
 our @EXPORT = qw(
+    notifyBuildStarted
     notifyBuildFinished);
 
+sub notifyBuildStarted {
+    my ($plugins, $build) = @_;
+    foreach my $plugin (@{$plugins}) {
+        eval {
+            $plugin->buildStarted($build);
+        };
+        if ($@) {
+            print STDERR "$plugin->buildStarted: $@\n":
+        }
+    }
+}
+
 sub notifyBuildFinished {
     my ($plugins, $build, $dependents) = @_;
     foreach my $plugin (@{$plugins}) {
diff --git a/src/lib/Hydra/Plugin.pm b/src/lib/Hydra/Plugin.pm
index 4a8ef69e..7783fb9e 100644
--- a/src/lib/Hydra/Plugin.pm
+++ b/src/lib/Hydra/Plugin.pm
@@ -20,6 +20,11 @@ sub instantiate {
     return @$plugins;
 }
 
+# Called when build $build has started.
+sub buildStarted {
+    my ($self, $build) = @_;
+}
+
 # Called when build $build has finished.  If the build failed, then
 # $dependents is an array ref to a list of builds that have also
 # failed as a result (i.e. because they depend on $build or a failed
diff --git a/src/script/hydra-notify b/src/script/hydra-notify
index 1e68dde7..4ecce21b 100755
--- a/src/script/hydra-notify
+++ b/src/script/hydra-notify
@@ -15,12 +15,12 @@ my $db = Hydra::Model::DB->new();
 
 my @plugins = Hydra::Plugin->instantiate(db => $db, config => $config);
 
-my $cmd = shift @ARGV or die "Syntax: hydra-notify build BUILD-ID [BUILD-IDs...]\n";
+my $cmd = shift @ARGV or die "Syntax: hydra-notify CMD BUILD-ID [BUILD-IDs...]\n";
 
-if ($cmd eq "build") {
-    my $buildId = shift @ARGV or die;
-    my $build = $db->resultset('Builds')->find($buildId)
-        or die "build $buildId does not exist\n";
+my $buildId = shift @ARGV or die;
+my $build = $db->resultset('Builds')->find($buildId)
+    or die "build $buildId does not exist\n";
+if ($cmd eq "build-finished") {
     my @dependents;
     foreach my $id (@ARGV) {
         my $dep = $db->resultset('Builds')->find($id)
@@ -28,6 +28,8 @@ if ($cmd eq "build") {
         push @dependents, $dep;
     }
     notifyBuildFinished(\@plugins, $build, [@dependents]);
+} elsif ($cmd eq "build-started") {
+    notifyBuildStarted(\@plugins, $build);
 }
 
 else {