diff --git a/mkdocs-website/docs/en/changelog.md b/mkdocs-website/docs/en/changelog.md
index fa3a3f838..ade489210 100644
--- a/mkdocs-website/docs/en/changelog.md
+++ b/mkdocs-website/docs/en/changelog.md
@@ -43,6 +43,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix failing Windows build due to unknown option by [thomas-senechal](https://github.com/thomas-senechal) in PR [#3208](https://github.com/wailsapp/wails/pull/3208)
 - Fix wrong baseURL when open window twice by @5aaee9 in PR [#3273](https://github.com/wailsapp/wails/pull/3273)
 - Fix ordering of if branches in `WebviewWindow.Restore` method by [@fbbdev](https://github.com/fbbdev) in [#3279](https://github.com/wailsapp/wails/pull/3279)
+- Correctly compute `startURL` across multiple `GetStartURL` invocations when `FRONTEND_DEVSERVER_URL` is present. [#3299](https://github.com/wailsapp/wails/pull/3299)
 
 ### Changed
 
diff --git a/v3/internal/assetserver/assetserver.go b/v3/internal/assetserver/assetserver.go
index 0d80007e7..24b049224 100644
--- a/v3/internal/assetserver/assetserver.go
+++ b/v3/internal/assetserver/assetserver.go
@@ -148,26 +148,19 @@ func GetStartURL(userURL string) (string, error) {
 		}
 		port := parsedURL.Port()
 		if port != "" {
-			baseURL.Host = net.JoinHostPort(baseURL.Host, port)
+			baseURL.Host = net.JoinHostPort(baseURL.Hostname(), port)
 			startURL = baseURL.String()
 		}
-	} else {
-		if userURL != "" {
-			// parse the url
-			parsedURL, err := url.Parse(userURL)
-			if err != nil {
-				return "", fmt.Errorf("Error parsing URL: " + err.Error())
-			}
-			if parsedURL.Scheme == "" {
-				startURL = baseURL.ResolveReference(&url.URL{Path: userURL}).String()
-				// if the original URL had a trailing slash, add it back
-				if strings.HasSuffix(userURL, "/") && !strings.HasSuffix(startURL, "/") {
-					startURL = startURL + "/"
-				}
-			} else {
-				startURL = userURL
-			}
-		}
 	}
+
+	if userURL != "" {
+		parsedURL, err := baseURL.Parse(userURL)
+		if err != nil {
+			return "", fmt.Errorf("Error parsing URL: " + err.Error())
+		}
+
+		startURL = parsedURL.String()
+	}
+
 	return startURL, nil
 }