diff --git a/src/main/java/de/mlessmann/certassist/models/Certificate.java b/src/main/java/de/mlessmann/certassist/models/Certificate.java
index 8213156..fdf3d16 100644
--- a/src/main/java/de/mlessmann/certassist/models/Certificate.java
+++ b/src/main/java/de/mlessmann/certassist/models/Certificate.java
@@ -29,7 +29,14 @@ public class Certificate {
 
     private String trustingAuthority;
 
-    @Min(1)
+    /**
+     * <ul>
+     *     <li>-1 = no requested key length is known (might happen with imported certificates)</li>
+     *     <li>0 = no key is available for this certificate (might happen with trusted third party certificates)</li>
+     *     <li>> 1 = The key length in bits used for the private key of this certificate</li>
+     * </ul>
+     */
+    @Min(-1)
     private int requestedKeyLength;
 
     private OffsetDateTime notBefore;
diff --git a/src/main/java/de/mlessmann/certassist/openssl/X509CertificateInfo.java b/src/main/java/de/mlessmann/certassist/openssl/X509CertificateInfo.java
index 51a53ff..d99d506 100644
--- a/src/main/java/de/mlessmann/certassist/openssl/X509CertificateInfo.java
+++ b/src/main/java/de/mlessmann/certassist/openssl/X509CertificateInfo.java
@@ -32,4 +32,8 @@ public record X509CertificateInfo(
         }
         return Collections.unmodifiableList(extensions);
     }
+
+    public boolean hasExtensions() {
+        return extensions != null && !extensions.isEmpty();
+    }
 }
diff --git a/src/main/java/de/mlessmann/certassist/service/CertificateCreationService.java b/src/main/java/de/mlessmann/certassist/service/CertificateCreationService.java
index 1b1476a..349558a 100644
--- a/src/main/java/de/mlessmann/certassist/service/CertificateCreationService.java
+++ b/src/main/java/de/mlessmann/certassist/service/CertificateCreationService.java
@@ -87,7 +87,9 @@ public class CertificateCreationService {
             )
         );
         certificate.setSubjectCommonName(info.subject().getCommonName());
-        certificate.setTrustingAuthority(info.issuer().getCommonName());
+        if (info.issuer() != null) {
+            certificate.setTrustingAuthority(info.issuer().getCommonName());
+        }
         certificate.setRequestedKeyLength(-1);
         certificate.setNotBefore(info.notBefore());
         certificate.setNotAfter(info.notAfter());
@@ -100,12 +102,14 @@ public class CertificateCreationService {
         certificate.setSubjectState(subjectInfo.getState());
         certificate.setSubjectLocality(subjectInfo.getLocality());
 
-        final CertificateInfoExtension extension = info.extensions().getFirst();
-        if (extension != null) {
-            final CertificateExtension certificateExtension = new CertificateExtension();
-            certificateExtension.setIdentifier("alternativeNames");
-            certificateExtension.setValue(String.join(",", extension.getAlternativeDnsNames()));
-            certificate.setCertificateExtension(List.of(certificateExtension));
+        if (info.hasExtensions()) {
+            final CertificateInfoExtension extension = info.extensions().getFirst();
+            if (extension != null) {
+                final CertificateExtension certificateExtension = new CertificateExtension();
+                certificateExtension.setIdentifier("alternativeNames");
+                certificateExtension.setValue(String.join(",", extension.getAlternativeDnsNames()));
+                certificate.setCertificateExtension(List.of(certificateExtension));
+            }
         }
         return certificate;
     }
@@ -119,6 +123,7 @@ public class CertificateCreationService {
         try {
             String fingerprint = openSSLService.getCertificateFingerprint(certificate);
             Certificate entity = createEntityFromInfo(openSSLService.getCertificateInfo(certificate));
+            entity.setRequestedKeyLength(-1);
             entity.setFingerprint(fingerprint);
             entity.setCert(Files.readAllBytes(certificate));
             if (keyFile != null) {