diff --git a/src/main/java/moe/yushi/authlibinjector/AuthlibInjector.java b/src/main/java/moe/yushi/authlibinjector/AuthlibInjector.java
index 4919f6f..972e741 100644
--- a/src/main/java/moe/yushi/authlibinjector/AuthlibInjector.java
+++ b/src/main/java/moe/yushi/authlibinjector/AuthlibInjector.java
@@ -98,6 +98,8 @@ public final class AuthlibInjector {
 	private static Optional<YggdrasilConfiguration> configure() {
 		String apiRoot = System.getProperty(PROP_API_ROOT);
 		if (apiRoot == null) return empty();
+
+		apiRoot = appendSuffixSlash(apiRoot);
 		Logging.CONFIG.info("API root: " + apiRoot);
 		warnIfHttp(apiRoot);
 
@@ -145,6 +147,14 @@ public final class AuthlibInjector {
 		}
 	}
 
+	private static String appendSuffixSlash(String url) {
+		if (!url.endsWith("/")) {
+			return url + "/";
+		} else {
+			return url;
+		}
+	}
+
 	private static ClassTransformer createTransformer(YggdrasilConfiguration config) {
 		ClassTransformer transformer = new ClassTransformer();
 		transformer.debugSaveClass = "true".equals(System.getProperty(PROP_DUMP_CLASS));
diff --git a/src/main/java/moe/yushi/authlibinjector/YggdrasilConfiguration.java b/src/main/java/moe/yushi/authlibinjector/YggdrasilConfiguration.java
index 3992266..1f8c64d 100644
--- a/src/main/java/moe/yushi/authlibinjector/YggdrasilConfiguration.java
+++ b/src/main/java/moe/yushi/authlibinjector/YggdrasilConfiguration.java
@@ -24,8 +24,6 @@ import moe.yushi.authlibinjector.util.KeyUtils;
 public class YggdrasilConfiguration {
 
 	public static YggdrasilConfiguration parse(String apiRoot, String metadataResponse) throws UncheckedIOException {
-		if (!apiRoot.endsWith("/")) apiRoot += "/";
-
 		JSONObject response = asJsonObject(parseJson(metadataResponse));
 
 		List<String> skinDomains =