diff --git a/config/http_config.go b/config/http_config.go
index 6060a093..07b389eb 100644
--- a/config/http_config.go
+++ b/config/http_config.go
@@ -111,9 +111,6 @@ type HTTPClientConfig struct {
 	ProxyURL URL `yaml:"proxy_url,omitempty"`
 	// TLSConfig to use to connect to the targets.
 	TLSConfig TLSConfig `yaml:"tls_config,omitempty"`
-	// Used to make sure that the configuration is valid and that BearerToken to
-	// Authorization.Credentials change has been handled.
-	valid bool
 }
 
 // SetDirectory joins any relative file paths with dir.
@@ -169,8 +166,6 @@ func (c *HTTPClientConfig) Validate() error {
 			c.BearerTokenFile = ""
 		}
 	}
-
-	c.valid = true
 	return nil
 }
 
@@ -207,12 +202,6 @@ func NewClientFromConfig(cfg HTTPClientConfig, name string, disableKeepAlives, e
 // NewRoundTripperFromConfig returns a new HTTP RoundTripper configured for the
 // given config.HTTPClientConfig. The name is used as go-conntrack metric label.
 func NewRoundTripperFromConfig(cfg HTTPClientConfig, name string, disableKeepAlives, enableHTTP2 bool) (http.RoundTripper, error) {
-	// Make sure that the configuration is valid.
-	if !cfg.valid {
-		if err := cfg.Validate(); err != nil {
-			return nil, err
-		}
-	}
 	newRT := func(tlsConfig *tls.Config) (http.RoundTripper, error) {
 		// The only timeout we care about is the configured scrape timeout.
 		// It is applied on request. So we leave out any timings here.
@@ -254,6 +243,13 @@ func NewRoundTripperFromConfig(cfg HTTPClientConfig, name string, disableKeepAli
 		} else if cfg.Authorization != nil && len(cfg.Authorization.CredentialsFile) > 0 {
 			rt = NewAuthorizationCredentialsFileRoundTripper(cfg.Authorization.Type, cfg.Authorization.CredentialsFile, rt)
 		}
+		// Backwards compatibility, be nice with importers who would not have
+		// called Validate().
+		if len(cfg.BearerToken) > 0 {
+			rt = NewAuthorizationCredentialsRoundTripper("Bearer", cfg.BearerToken, rt)
+		} else if len(cfg.BearerTokenFile) > 0 {
+			rt = NewAuthorizationCredentialsFileRoundTripper("Bearer", cfg.BearerTokenFile, rt)
+		}
 
 		if cfg.BasicAuth != nil {
 			rt = NewBasicAuthRoundTripper(cfg.BasicAuth.Username, cfg.BasicAuth.Password, cfg.BasicAuth.PasswordFile, rt)
diff --git a/config/http_config_test.go b/config/http_config_test.go
index d0cdee8c..a35ae895 100644
--- a/config/http_config_test.go
+++ b/config/http_config_test.go
@@ -306,6 +306,10 @@ func TestNewClientFromConfig(t *testing.T) {
 		}
 		defer testServer.Close()
 
+		err = validConfig.clientConfig.Validate()
+		if err != nil {
+			t.Fatal(err.Error())
+		}
 		client, err := NewClientFromConfig(validConfig.clientConfig, "test", false, true)
 		if err != nil {
 			t.Errorf("Can't create a client from this config: %+v", validConfig.clientConfig)