diff --git a/server/hook.go b/server/hook.go
index ee50c3991..5c145455f 100644
--- a/server/hook.go
+++ b/server/hook.go
@@ -177,6 +177,11 @@ func PostHook(c *gin.Context) {
 		return
 	}
 
+	if zeroSteps(*build, remoteYamlConfigs) {
+		c.String(200, "Step conditions yield zero runnable steps")
+		return
+	}
+
 	// update some build fields
 	build.RepoID = repo.ID
 	build.Verified = true
@@ -293,6 +298,30 @@ func branchFiltered(build *model.Build, remoteYamlConfigs []*remote.FileMeta) bo
 	return true
 }
 
+// uses pass by value as procBuilder has side effects on build. Something to be fixed
+func zeroSteps(build model.Build, remoteYamlConfigs []*remote.FileMeta) bool {
+	b := procBuilder{
+		Repo:  &model.Repo{},
+		Curr:  &build,
+		Last:  &model.Build{},
+		Netrc: &model.Netrc{},
+		Secs:  []*model.Secret{},
+		Regs:  []*model.Registry{},
+		Link:  "",
+		Yamls: remoteYamlConfigs,
+	}
+
+	buildItems, err := b.Build()
+	if err != nil {
+		return false
+	}
+	if len(buildItems) == 0 {
+		return true
+	}
+
+	return false
+}
+
 func findOrPersistPipelineConfig(build *model.Build, remoteYamlConfig *remote.FileMeta) (*model.Config, error) {
 	sha := shasum(remoteYamlConfig.Data)
 	conf, err := Config.Storage.Config.ConfigFindIdentical(build.RepoID, sha)
diff --git a/server/procBuilder.go b/server/procBuilder.go
index 5eaadeefa..a78318d90 100644
--- a/server/procBuilder.go
+++ b/server/procBuilder.go
@@ -59,7 +59,9 @@ func (b *procBuilder) Build() ([]*buildItem, error) {
 
 	sort.Sort(remote.ByName(b.Yamls))
 
-	for j, y := range b.Yamls {
+	pidSequence := 1
+
+	for _, y := range b.Yamls {
 		// matrix axes
 		axes, err := matrix.ParseString(string(y.Data))
 		if err != nil {
@@ -69,16 +71,15 @@ func (b *procBuilder) Build() ([]*buildItem, error) {
 			axes = append(axes, matrix.Axis{})
 		}
 
-		for i, axis := range axes {
+		for _, axis := range axes {
 			proc := &model.Proc{
 				BuildID: b.Curr.ID,
-				PID:     j + i + 1,
-				PGID:    j + i + 1,
+				PID:     pidSequence,
+				PGID:    pidSequence,
 				State:   model.StatusPending,
 				Environ: axis,
 				Name:    sanitizePath(y.Name),
 			}
-			b.Curr.Procs = append(b.Curr.Procs, proc)
 
 			metadata := metadataFromStruct(b.Repo, b.Curr, b.Last, proc, b.Link)
 			environ := b.environmentVariables(metadata, axis)
@@ -111,6 +112,10 @@ func (b *procBuilder) Build() ([]*buildItem, error) {
 
 			ir := b.toInternalRepresentation(parsed, environ, metadata, proc.ID)
 
+			if len(ir.Stages) == 0 {
+				continue
+			}
+
 			item := &buildItem{
 				Proc:      proc,
 				Config:    ir,
@@ -122,7 +127,10 @@ func (b *procBuilder) Build() ([]*buildItem, error) {
 			if item.Labels == nil {
 				item.Labels = map[string]string{}
 			}
+
+			b.Curr.Procs = append(b.Curr.Procs, proc)
 			items = append(items, item)
+			pidSequence++
 		}
 	}
 
diff --git a/server/procBuilder_test.go b/server/procBuilder_test.go
index 4452dfaf4..1c456cc29 100644
--- a/server/procBuilder_test.go
+++ b/server/procBuilder_test.go
@@ -201,6 +201,78 @@ pipeline:
 		}
 	}
 	if buildItems[1].Proc.State != model.StatusPending {
-		t.Fatal("Should not run on dev branch")
+		t.Fatal("Should run on dev branch")
+	}
+}
+
+func TestZeroSteps(t *testing.T) {
+	build := &model.Build{Branch: "dev"}
+
+	b := procBuilder{
+		Repo:  &model.Repo{},
+		Curr:  build,
+		Last:  &model.Build{},
+		Netrc: &model.Netrc{},
+		Secs:  []*model.Secret{},
+		Regs:  []*model.Registry{},
+		Link:  "",
+		Yamls: []*remote.FileMeta{
+			&remote.FileMeta{Data: []byte(`
+skip_clone: true
+pipeline:
+  build:
+    when:
+      branch: notdev
+    image: scratch
+    yyy: ${DRONE_COMMIT_MESSAGE}
+`)},
+		},
+	}
+
+	buildItems, err := b.Build()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(buildItems) != 0 {
+		t.Fatal("Should not generate a build item if there are no steps")
+	}
+	if len(build.Procs) != 0 {
+		t.Fatal("Should not generate a build item if there are no steps")
+	}
+}
+
+func TestTree(t *testing.T) {
+	build := &model.Build{}
+
+	b := procBuilder{
+		Repo:  &model.Repo{},
+		Curr:  build,
+		Last:  &model.Build{},
+		Netrc: &model.Netrc{},
+		Secs:  []*model.Secret{},
+		Regs:  []*model.Registry{},
+		Link:  "",
+		Yamls: []*remote.FileMeta{
+			&remote.FileMeta{Data: []byte(`
+pipeline:
+  build:
+    image: scratch
+    yyy: ${DRONE_COMMIT_MESSAGE}
+`)},
+		},
+	}
+
+	_, err := b.Build()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(build.Procs) != 3 {
+		t.Fatal("Should generate three in total")
+	}
+	if build.Procs[1].PPID != 1 {
+		t.Fatal("Clone step should be a children of the stage")
+	}
+	if build.Procs[2].PPID != 1 {
+		t.Fatal("Build step should be a children of the stage")
 	}
 }