diff --git a/server/builds.go b/server/builds.go
index 265c36d4..6c6213db 100644
--- a/server/builds.go
+++ b/server/builds.go
@@ -1,7 +1,10 @@
 package server
 
 import (
+	"fmt"
 	"io"
+	"net/http"
+	"net/url"
 	"strconv"
 	"time"
 
@@ -239,5 +242,21 @@ func KillBuild(c *gin.Context) {
 		return
 	}
 
+	// get the agent from the repository so we can
+	// notify the agent to kill the build.
+	agent, err := store.BuildAgent(repo.FullName, build.Number)
+	if err != nil {
+		c.JSON(200, build)
+		return
+	}
+	url_, _ := url.Parse("http://" + agent.Addr)
+	url_.Path = fmt.Sprintf("/cancel/%s/%v", repo.FullName, build.Number)
+	resp, err := http.Post(url_.String(), "application/json", nil)
+	if err != nil {
+		c.Fail(500, err)
+		return
+	}
+	defer resp.Body.Close()
+
 	c.JSON(200, build)
 }
diff --git a/server/static/scripts/views/build.html b/server/static/scripts/views/build.html
index 0d141216..1e634a62 100644
--- a/server/static/scripts/views/build.html
+++ b/server/static/scripts/views/build.html
@@ -3,8 +3,8 @@
 <a href="/{{ repo.full_name }}">Back</a>
 
 <div>
-	<button ng-if="build.state !== 'pending' && build.state !== 'started'" ng-click="restart()">Restart</button>
-	<button ng-if="build.state === 'pending' || build.state === 'started'" ng-click="cancel()">Cancel</button>
+	<button ng-if="build.state !== 'pending' && build.state !== 'running'" ng-click="restart()">Restart</button>
+	<button ng-if="build.state === 'pending' || build.state === 'running'" ng-click="cancel()">Cancel</button>
 </div>
 
 <dl>