diff --git a/serve.go b/serve.go
index d30973ad..858973c7 100644
--- a/serve.go
+++ b/serve.go
@@ -186,5 +186,9 @@ func (h healthHandler) responseContentType(outputName string) string {
 	if outputName == "json" {
 		return "application/json"
 	}
+	if outputName == "prometheus" {
+		return "text/plain; version=0.0.4"
+	}
+
 	return fmt.Sprintf("%s%s", mediaTypePrefix, outputName)
 }
diff --git a/serve_test.go b/serve_test.go
index 8b19d048..c7f64a26 100644
--- a/serve_test.go
+++ b/serve_test.go
@@ -117,6 +117,15 @@ func TestServeNegotiatingContent(t *testing.T) {
 			expectedHTTPStatus:  http.StatusOK,
 			expectedContentType: "application/json",
 		},
+		"accept prometheus": {
+			acceptHeader: []string{
+				"text/plain; version=0.0.4",
+			},
+			outputFormat:        "prometheus",
+			specFile:            filepath.Join("testdata", "passing.goss.yaml"),
+			expectedHTTPStatus:  http.StatusOK,
+			expectedContentType: "text/plain; version=0.0.4",
+		},
 		"accept header contains vendor-specific output format different from process-level": {
 			acceptHeader: []string{
 				"application/vnd.goss-rspecish",