diff --git a/src/main/java/de/mlessmann/certassist/openssl/OpenSSLCertificateCreator.java b/src/main/java/de/mlessmann/certassist/openssl/OpenSSLCertificateCreator.java
index 5a994e2..74af6ab 100644
--- a/src/main/java/de/mlessmann/certassist/openssl/OpenSSLCertificateCreator.java
+++ b/src/main/java/de/mlessmann/certassist/openssl/OpenSSLCertificateCreator.java
@@ -393,8 +393,9 @@ public class OpenSSLCertificateCreator {
             throw new RuntimeException(e);
         }
 
+        StartedProcess certGenProc = null;
         try {
-            StartedProcess certGenProc = new ProcessExecutor()
+            certGenProc = new ProcessExecutor()
                 .command(
                     resolveOpenSSL(),
                     "x509",
@@ -421,6 +422,8 @@ public class OpenSSLCertificateCreator {
             throw new CommandLineOperationException("Failure running OpenSSL x509 command.", e);
         } catch (ExecutionException e) {
             throw new RuntimeException(e);
+        } finally {
+            killIfActive(certGenProc);
         }
         return outFile;
     }