diff --git a/.circleci/config.yml b/.circleci/config.yml
index 1ea616bfac..f9ff897626 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -448,7 +448,7 @@ jobs:
           # Currently all integration tests are in a single directory.
           command: |
             cd ~/go/src/github.com/stellar/go
-            go test -timeout 25m -v ./services/horizon/internal/integration/...
+            go test -race -timeout 25m -v ./services/horizon/internal/integration/...
 
 #-------------------------------------------------------------------------#
 # Workflows orchestrate jobs and make sure they run in the right sequence #
diff --git a/clients/horizonclient/CHANGELOG.md b/clients/horizonclient/CHANGELOG.md
index d2b82373ab..b25b1d033b 100644
--- a/clients/horizonclient/CHANGELOG.md
+++ b/clients/horizonclient/CHANGELOG.md
@@ -7,6 +7,7 @@ file.  This project adheres to [Semantic Versioning](http://semver.org/).
 
 * Added transaction and operation result codes to the horizonclient.Error string for easy glancing at string only errors for underlying cause.
 * Fix bug in the transaction submission where requests with large transaction payloads fail with an HTTP 414 URI Too Long error ([#3643](https://github.com/stellar/go/pull/3643)).
+* Fix a data race in `Client.fixHorizonURL`([#3690](https://github.com/stellar/go/pull/3690)).
 
 ## [v7.0.0](https://github.com/stellar/go/releases/tag/horizonclient-v7.0.0) - 2021-05-15
 
diff --git a/clients/horizonclient/client.go b/clients/horizonclient/client.go
index 7add6a02fd..3d0c9c56b2 100644
--- a/clients/horizonclient/client.go
+++ b/clients/horizonclient/client.go
@@ -26,8 +26,7 @@ import (
 
 // sendRequest builds the URL for the given horizon request and sends the url to a horizon server
 func (c *Client) sendRequest(hr HorizonRequest, resp interface{}) (err error) {
-	c.HorizonURL = c.fixHorizonURL()
-	req, err := hr.HTTPRequest(c.HorizonURL)
+	req, err := hr.HTTPRequest(c.fixHorizonURL())
 	if err != nil {
 		return err
 	}
@@ -270,7 +269,10 @@ func (c *Client) setDefaultClient() {
 
 // fixHorizonURL strips all slashes(/) at the end of HorizonURL if any, then adds a single slash
 func (c *Client) fixHorizonURL() string {
-	return strings.TrimRight(c.HorizonURL, "/") + "/"
+	c.fixHorizonURLOnce.Do(func() {
+		c.HorizonURL = strings.TrimRight(c.HorizonURL, "/") + "/"
+	})
+	return c.HorizonURL
 }
 
 // SetHorizonTimeout allows users to set the timeout before a horizon request is cancelled.
diff --git a/clients/horizonclient/main.go b/clients/horizonclient/main.go
index aeb8b6dddb..c81572dd71 100644
--- a/clients/horizonclient/main.go
+++ b/clients/horizonclient/main.go
@@ -129,7 +129,8 @@ type UniversalTimeHandler func() int64
 // Client struct contains data for creating a horizon client that connects to the stellar network.
 type Client struct {
 	// URL of Horizon server to connect
-	HorizonURL string
+	HorizonURL        string
+	fixHorizonURLOnce sync.Once
 
 	// HTTP client to make requests with
 	HTTP HTTP
diff --git a/services/horizon/internal/actions/helpers.go b/services/horizon/internal/actions/helpers.go
index 59d5e8410d..57ed199838 100644
--- a/services/horizon/internal/actions/helpers.go
+++ b/services/horizon/internal/actions/helpers.go
@@ -399,7 +399,6 @@ func getParams(dst interface{}, r *http.Request) error {
 		}
 	}
 
-	decoder.IgnoreUnknownKeys(true)
 	if err := decoder.Decode(dst, query); err != nil {
 		for k, e := range err.(schema.MultiError) {
 			return problem.NewProblemWithInvalidField(
@@ -609,3 +608,7 @@ func countNonEmpty(params ...interface{}) (int, error) {
 
 	return count, nil
 }
+
+func init() {
+	decoder.IgnoreUnknownKeys(true)
+}