diff --git a/cmd/prometheus/config.go b/cmd/prometheus/config.go
index 19858d1cd..35f8c0b8d 100644
--- a/cmd/prometheus/config.go
+++ b/cmd/prometheus/config.go
@@ -242,10 +242,12 @@ func parse(args []string) error {
 	if err := parsePrometheusURL(); err != nil {
 		return err
 	}
-
 	if err := parseInfluxdbURL(); err != nil {
 		return err
 	}
+	if err := validateAlertmanagerURL(); err != nil {
+		return err
+	}
 
 	cfg.remote.InfluxdbPassword = os.Getenv("INFLUXDB_PW")
 
@@ -266,7 +268,7 @@ func parsePrometheusURL() error {
 	}
 
 	if ok := govalidator.IsURL(cfg.prometheusURL); !ok {
-		return fmt.Errorf("Invalid Prometheus URL: %s", cfg.prometheusURL)
+		return fmt.Errorf("invalid Prometheus URL: %s", cfg.prometheusURL)
 	}
 
 	promURL, err := url.Parse(cfg.prometheusURL)
@@ -289,7 +291,7 @@ func parseInfluxdbURL() error {
 	}
 
 	if ok := govalidator.IsURL(cfg.influxdbURL); !ok {
-		return fmt.Errorf("Invalid InfluxDB URL: %s", cfg.influxdbURL)
+		return fmt.Errorf("invalid InfluxDB URL: %s", cfg.influxdbURL)
 	}
 
 	url, err := url.Parse(cfg.influxdbURL)
@@ -301,6 +303,23 @@ func parseInfluxdbURL() error {
 	return nil
 }
 
+func validateAlertmanagerURL() error {
+	if cfg.notifier.AlertmanagerURL == "" {
+		return nil
+	}
+	if ok := govalidator.IsURL(cfg.notifier.AlertmanagerURL); !ok {
+		return fmt.Errorf("invalid Alertmanager URL: %s", cfg.notifier.AlertmanagerURL)
+	}
+	url, err := url.Parse(cfg.notifier.AlertmanagerURL)
+	if err != nil {
+		return err
+	}
+	if url.Scheme == "" {
+		return fmt.Errorf("missing scheme in Alertmanager URL: %s", cfg.notifier.AlertmanagerURL)
+	}
+	return nil
+}
+
 var helpTmpl = `
 usage: prometheus [<args>]
 {{ range $cat, $flags := . }}{{ if ne $cat "." }} == {{ $cat | upper }} =={{ end }}
diff --git a/cmd/prometheus/config_test.go b/cmd/prometheus/config_test.go
index 4f5e8c112..a77eaf207 100644
--- a/cmd/prometheus/config_test.go
+++ b/cmd/prometheus/config_test.go
@@ -48,6 +48,18 @@ func TestParse(t *testing.T) {
 			input: []string{"-storage.remote.influxdb-url", "'https://some-url/'"},
 			valid: false,
 		},
+		{
+			input: []string{"-alertmanager.url", ""},
+			valid: true,
+		},
+		{
+			input: []string{"-alertmanager.url", "http://alertmanager.company.com"},
+			valid: true,
+		},
+		{
+			input: []string{"-alertmanager.url", "alertmanager.company.com"},
+			valid: false,
+		},
 	}
 
 	for i, test := range tests {