diff --git a/pom.xml b/pom.xml
index 5ce5dbc..87b9804 100644
--- a/pom.xml
+++ b/pom.xml
@@ -5,8 +5,8 @@
   	<version>0.1.9-SNAPSHOT</version>
 
   	<properties>
-    	<maven.compiler.source>17</maven.compiler.source>
-    	<maven.compiler.target>17</maven.compiler.target>
+    	<maven.compiler.source>11</maven.compiler.source>
+    	<maven.compiler.target>11</maven.compiler.target>
   	</properties>
 
 	<licenses>
diff --git a/src/main/java/eu/m724/jarupdater/verify/SignatureVerifierImpl.java b/src/main/java/eu/m724/jarupdater/verify/SignatureVerifierImpl.java
index d879713..9f1c80d 100644
--- a/src/main/java/eu/m724/jarupdater/verify/SignatureVerifierImpl.java
+++ b/src/main/java/eu/m724/jarupdater/verify/SignatureVerifierImpl.java
@@ -100,7 +100,8 @@ public class SignatureVerifierImpl {
                     for (CodeSigner signer : signers) {
                         for (Certificate cert : signer.getSignerCertPath().getCertificates()) {
                             PublicKey certPublicKey = cert.getPublicKey();
-                            if (certPublicKey instanceof RSAPublicKey rsaKey) {
+                            if (certPublicKey instanceof RSAPublicKey) {
+                                RSAPublicKey rsaKey = (RSAPublicKey) certPublicKey;
                                 signerPublicKeys.add(Base64.getEncoder().encodeToString(rsaKey.getEncoded()));
 
                                 for (RSAPublicKey publicKey : publicKeys) {