diff --git a/compiler/native/expand_test.go b/compiler/native/expand_test.go
index f7aaf7b4d..ca85ef618 100644
--- a/compiler/native/expand_test.go
+++ b/compiler/native/expand_test.go
@@ -458,10 +458,10 @@ func TestNative_ExpandStepsWarnings(t *testing.T) {
 	}
 
 	wantWarnings := []string{
-		"warnings:25:duplicate << keys in single YAML map",
-		"warnings:32:duplicate << keys in single YAML map",
-		"warnings:44:duplicate << keys in single YAML map",
-		"warnings:43:duplicate << keys in single YAML map",
+		"[warnings]:25:duplicate << keys in single YAML map",
+		"[warnings]:32:duplicate << keys in single YAML map",
+		"[warnings]:44:duplicate << keys in single YAML map",
+		"[warnings]:43:duplicate << keys in single YAML map",
 	}
 
 	// run test
diff --git a/internal/yaml.go b/internal/yaml.go
index afac0abea..ef621df6a 100644
--- a/internal/yaml.go
+++ b/internal/yaml.go
@@ -23,7 +23,7 @@ func ParseYAML(data []byte, tmplName string) (*types.Build, []string, error) {
 	)
 
 	if len(tmplName) > 0 {
-		warningPrefix = fmt.Sprintf("%s:", tmplName)
+		warningPrefix = fmt.Sprintf("[%s]:", tmplName)
 	}
 
 	err := yaml.Unmarshal(data, &rootNode)
diff --git a/internal/yaml_test.go b/internal/yaml_test.go
index 2b0401109..3ee72f9c0 100644
--- a/internal/yaml_test.go
+++ b/internal/yaml_test.go
@@ -76,7 +76,7 @@ func TestInternal_ParseYAML(t *testing.T) {
 			name:          "anchor collapse - warning prefix",
 			file:          "testdata/buildkite_new_version.yml",
 			wantBuild:     wantBuild,
-			wantWarnings:  []string{"prefix:16:duplicate << keys in single YAML map"},
+			wantWarnings:  []string{"[prefix]:16:duplicate << keys in single YAML map"},
 			warningPrefix: "prefix",
 		},
 		{