diff --git a/src/github.com/matrix-org/go-neb/services/circleci/circleci.go b/src/github.com/matrix-org/go-neb/services/circleci/circleci.go
index a29240a..5f856c5 100644
--- a/src/github.com/matrix-org/go-neb/services/circleci/circleci.go
+++ b/src/github.com/matrix-org/go-neb/services/circleci/circleci.go
@@ -22,8 +22,8 @@ const ServiceType = "circleci"
 
 // DefaultTemplate contains the template that will be used if none is supplied.
 // This matches the default mentioned at: https://docs.travis-ci.com/user/notifications#Customizing-slack-notifications
-const DefaultTemplate = (`%{repository_slug}#%{buildnum} (%{branch} - %{commit} : %{committername}): %{outcome}
-	Build details : %{buildurl}`)
+const DefaultTemplate = (`%{repository_slug}#%{build_num} (%{branch} - %{commit} : %{committer_name}): %{outcome}
+	Build details : %{build_url}`)
 
 // Matches 'owner/repo'
 var ownerRepoRegex = regexp.MustCompile(`^([A-z0-9-_.]+)/([A-z0-9-_.]+)$`)
@@ -42,7 +42,7 @@ var httpClient = &http.Client{}
 //           "!ewfug483gsfe:localhost": {
 //               repos: {
 //                   "matrix-org/go-neb": {
-//                       template: "%{repository_slug}#%{buildnum} (%{branch} - %{commit} : %{committername}): %{outcome}\nBuild details : %{buildurl}"
+//                       template: "%{repository_slug}#%{build_num} (%{branch} - %{commit} : %{committer_name}): %{outcome}\nBuild details : %{build_url}"
 //                   }
 //               }
 //           }
@@ -62,20 +62,20 @@ type Service struct {
 			// This is identical to the format of Slack Notifications for Travis-CI:
 			// https://docs.travis-ci.com/user/notifications#Customizing-slack-notifications
 			//
-			// As this is CircleCI it also supports all CircleCI fields (full loiwer case no "_" )
+			// As this is CircleCI it also supports all CircleCI fields
 			// Compare with https://circleci.com/docs/api/v1-reference/#build
 			//
 			// The following variables are available:
 			//   repository_slug: your Git* repo identifier (like svenfuchs/minimal)
 			//   reponame: the slug without the username
 			//   repository_name: the slug without the username //Deprecated for CircleCI use "reponame" instead
-			//   buildnum: build number
-			//   build_number: build number //Deprecated for CircleCI use "buildnum" instead
+			//   build_num: build number
+			//   build_number: build number //Deprecated for CircleCI use "build_num" instead
 			//   build_id: build id //Deprecated for CircleCI use "build_num" instead as this value doesn't really exist in CircleCI
 			//   branch: branch build name
 			//   commit: shortened commit SHA
-			//   committername: commit author name
-			//   author: commit author name //Deprecated for CircleCI use "committername" instead
+			//   committer_name: commit author name
+			//   author: commit author name //Deprecated for CircleCI use "committer_name" instead
 			//   body: commit message of build
 			//   commit_message: commit message of build //Deprecated for CircleCI use "body" instead
 			//   commit_subject: first line of the commit message
@@ -83,8 +83,7 @@ type Service struct {
 			//   message: CircleCI message to the build
 			//   duration: total duration of all builds in the matrix
 			//   elapsed_time: time between build start and finish
-			//   buildurl: URL of the build detail
-			//   build_url: URL of the build detail //Deprecated for CircleCI use "buildurl" instead
+			//   build_url: URL of the build detail
 
 			Template string `json:"template"`
 		} `json:"repos"`
@@ -129,9 +128,9 @@ func notifToTemplate(n WebhookNotification) map[string]string {
 	for key, value := range rawT {
 		switch value := value.(type) {
 		case string:
-			t[strings.ToLower(key)] = value
+			t[CamelCaseToUnderscore(key)] = value
 		case int:
-			t[strings.ToLower(key)] = strconv.Itoa(value)
+			t[CamelCaseToUnderscore(key)] = strconv.Itoa(value)
 		}
 	}
 	return t
diff --git a/src/github.com/matrix-org/go-neb/services/circleci/circleci_test.go b/src/github.com/matrix-org/go-neb/services/circleci/circleci_test.go
index 69195b3..086ddc2 100644
--- a/src/github.com/matrix-org/go-neb/services/circleci/circleci_test.go
+++ b/src/github.com/matrix-org/go-neb/services/circleci/circleci_test.go
@@ -25,22 +25,22 @@ var circleciTests = []struct {
 }{
 	{
 		exampleBody,
-		"%{repository_slug}#%{buildnum} (%{branch} - %{commit} : %{committername}): %{outcome}",
+		"%{repository_slug}#%{build_num} (%{branch} - %{commit} : %{committer_name}): %{outcome}",
 		"circleci/mongofinil#22 (master - 1d231626ba : Allen Rohner): success",
 	},
 	{
 		exampleBody,
-		"%{repository_slug}#%{buildnum} (%{branch} - %{commit} : %{committername}): %{outcome}",
+		"%{repository_slug}#%{build_num} (%{branch} - %{commit} : %{committer_name}): %{outcome}",
 		"circleci/mongofinil#22 (master - 1d231626ba : Allen Rohner): success",
 	},
 	{
 		strings.TrimSuffix(exampleBody, "%7D") + "%2C%22EXTRA_KEY%22%3Anull%7D",
-		"%{repository_slug}#%{buildnum} (%{branch} - %{commit} : %{committername}): %{outcome}",
+		"%{repository_slug}#%{build_num} (%{branch} - %{commit} : %{committer_name}): %{outcome}",
 		"circleci/mongofinil#22 (master - 1d231626ba : Allen Rohner): success",
 	},
 	{
 		exampleBody,
-		"%{repository_slug}#%{buildnum} %{duration}",
+		"%{repository_slug}#%{build_num} %{duration}",
 		"circleci/mongofinil#22 23s",
 	},
 }
diff --git a/src/github.com/matrix-org/go-neb/services/circleci/util.go b/src/github.com/matrix-org/go-neb/services/circleci/util.go
new file mode 100644
index 0000000..d21e2c7
--- /dev/null
+++ b/src/github.com/matrix-org/go-neb/services/circleci/util.go
@@ -0,0 +1,61 @@
+package circleci
+
+import (
+	"unicode"
+	"unicode/utf8"
+)
+
+type buffer struct {
+	r         []byte
+	runeBytes [utf8.UTFMax]byte
+}
+
+func (b *buffer) write(r rune) {
+	if r < utf8.RuneSelf {
+		b.r = append(b.r, byte(r))
+		return
+	}
+	n := utf8.EncodeRune(b.runeBytes[0:], r)
+	b.r = append(b.r, b.runeBytes[0:n]...)
+}
+
+func (b *buffer) indent() {
+	if len(b.r) > 0 {
+		b.r = append(b.r, '_')
+	}
+}
+
+func CamelCaseToUnderscore(s string) string {
+	b := buffer{
+		r: make([]byte, 0, len(s)),
+	}
+	var m rune
+	var w bool
+	for _, ch := range s {
+		if unicode.IsUpper(ch) {
+			if m != 0 {
+				if !w {
+					b.indent()
+					w = true
+				}
+				b.write(m)
+			}
+			m = unicode.ToLower(ch)
+		} else {
+			if m != 0 {
+				b.indent()
+				b.write(m)
+				m = 0
+				w = false
+			}
+			b.write(ch)
+		}
+	}
+	if m != 0 {
+		if !w {
+			b.indent()
+		}
+		b.write(m)
+	}
+	return string(b.r)
+}
\ No newline at end of file