diff --git a/pgpainless-sop/src/main/java/org/pgpainless/sop/EncryptImpl.java b/pgpainless-sop/src/main/java/org/pgpainless/sop/EncryptImpl.java
index 3c5f8e8a..0843ae08 100644
--- a/pgpainless-sop/src/main/java/org/pgpainless/sop/EncryptImpl.java
+++ b/pgpainless-sop/src/main/java/org/pgpainless/sop/EncryptImpl.java
@@ -8,6 +8,8 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.nio.charset.Charset;
+import java.util.HashSet;
+import java.util.Set;
 
 import org.bouncycastle.openpgp.PGPException;
 import org.bouncycastle.openpgp.PGPPublicKeyRingCollection;
@@ -23,6 +25,8 @@ import org.pgpainless.encryption_signing.ProducerOptions;
 import org.pgpainless.encryption_signing.SigningOptions;
 import org.pgpainless.exception.KeyException;
 import org.pgpainless.exception.WrongPassphraseException;
+import org.pgpainless.key.OpenPgpFingerprint;
+import org.pgpainless.key.info.KeyRingInfo;
 import org.pgpainless.util.Passphrase;
 import sop.Ready;
 import sop.enums.EncryptAs;
@@ -35,6 +39,7 @@ public class EncryptImpl implements Encrypt {
     EncryptionOptions encryptionOptions = new EncryptionOptions();
     SigningOptions signingOptions = null;
     MatchMakingSecretKeyRingProtector protector = new MatchMakingSecretKeyRingProtector();
+    private final Set<PGPSecretKeyRing> signingKeys = new HashSet<>();
 
     private EncryptAs encryptAs = EncryptAs.Binary;
     boolean armor = true;
@@ -63,23 +68,15 @@ public class EncryptImpl implements Encrypt {
             if (keys.size() != 1) {
                 throw new SOPGPException.BadData(new AssertionError("Exactly one secret key at a time expected. Got " + keys.size()));
             }
-
             PGPSecretKeyRing signingKey = keys.iterator().next();
-            protector.addSecretKey(signingKey);
 
-            try {
-                signingOptions.addInlineSignature(
-                        protector,
-                        signingKey,
-                        (encryptAs == EncryptAs.Binary ? DocumentSignatureType.BINARY_DOCUMENT : DocumentSignatureType.CANONICAL_TEXT_DOCUMENT)
-                );
-            } catch (IllegalArgumentException e) {
-                throw new SOPGPException.KeyCannotSign();
-            } catch (WrongPassphraseException e) {
-                throw new SOPGPException.KeyIsProtected();
-            } catch (PGPException e) {
-                throw new SOPGPException.BadData(e);
+            KeyRingInfo info = PGPainless.inspectKeyRing(signingKey);
+            if (info.getSigningSubkeys().isEmpty()) {
+                throw new SOPGPException.KeyCannotSign("Key " + OpenPgpFingerprint.of(signingKey) + " cannot sign.");
             }
+
+            protector.addSecretKey(signingKey);
+            signingKeys.add(signingKey);
         } catch (IOException | PGPException e) {
             throw new SOPGPException.BadData(e);
         }
@@ -122,6 +119,22 @@ public class EncryptImpl implements Encrypt {
         producerOptions.setAsciiArmor(armor);
         producerOptions.setEncoding(encryptAsToStreamEncoding(encryptAs));
 
+        for (PGPSecretKeyRing signingKey : signingKeys) {
+            try {
+                signingOptions.addInlineSignature(
+                        protector,
+                        signingKey,
+                        (encryptAs == EncryptAs.Binary ? DocumentSignatureType.BINARY_DOCUMENT : DocumentSignatureType.CANONICAL_TEXT_DOCUMENT)
+                );
+            } catch (KeyException.UnacceptableSigningKeyException e) {
+                throw new SOPGPException.KeyCannotSign();
+            } catch (WrongPassphraseException e) {
+                throw new SOPGPException.KeyIsProtected();
+            } catch (PGPException e) {
+                throw new SOPGPException.BadData(e);
+            }
+        }
+
         try {
             ProxyOutputStream proxy = new ProxyOutputStream();
             EncryptionStream encryptionStream = PGPainless.encryptAndOrSign()
diff --git a/pgpainless-sop/src/test/java/org/pgpainless/sop/EncryptDecryptRoundTripTest.java b/pgpainless-sop/src/test/java/org/pgpainless/sop/EncryptDecryptRoundTripTest.java
index 45a26586..7bc5bfdb 100644
--- a/pgpainless-sop/src/test/java/org/pgpainless/sop/EncryptDecryptRoundTripTest.java
+++ b/pgpainless-sop/src/test/java/org/pgpainless/sop/EncryptDecryptRoundTripTest.java
@@ -38,6 +38,7 @@ public class EncryptDecryptRoundTripTest {
         sop = new SOPImpl();
         aliceKey = sop.generateKey()
                 .userId("Alice <alice@pgpainless.org>")
+                .withKeyPassword("wonderland.is.c00l")
                 .generate()
                 .getBytes();
         aliceCert = sop.extractCert()
@@ -56,6 +57,7 @@ public class EncryptDecryptRoundTripTest {
     public void basicRoundTripWithKey() throws IOException, SOPGPException.KeyCannotSign {
         byte[] encrypted = sop.encrypt()
                 .signWith(aliceKey)
+                .withKeyPassword("wonderland.is.c00l")
                 .withCert(aliceCert)
                 .withCert(bobCert)
                 .plaintext(message)
@@ -426,6 +428,15 @@ public class EncryptDecryptRoundTripTest {
         assertArrayEquals(message, bytesAndResult.getBytes());
     }
 
+    @Test
+    public void testEncryptWithWrongPassphraseThrowsKeyIsProtected() {
+        assertThrows(SOPGPException.KeyIsProtected.class, () -> sop.encrypt()
+                .withKeyPassword("falsePassphrase")
+                .signWith(aliceKey)
+                .withCert(bobCert)
+                .plaintext(message));
+    }
+
     @Test
     public void testDecryptionWithSessionKey_VerificationWithCert() throws IOException {
         byte[] plaintext = "This is a test message.\nSit back and relax.\n".getBytes(StandardCharsets.UTF_8);
diff --git a/pgpainless-sop/src/test/java/org/pgpainless/sop/IncapableKeysTest.java b/pgpainless-sop/src/test/java/org/pgpainless/sop/IncapableKeysTest.java
index a50acee1..5139bbf6 100644
--- a/pgpainless-sop/src/test/java/org/pgpainless/sop/IncapableKeysTest.java
+++ b/pgpainless-sop/src/test/java/org/pgpainless/sop/IncapableKeysTest.java
@@ -64,4 +64,9 @@ public class IncapableKeysTest {
         assertThrows(SOPGPException.KeyCannotSign.class, () -> sop.detachedSign().key(nonSigningKey));
         assertThrows(SOPGPException.KeyCannotSign.class, () -> sop.inlineSign().key(nonSigningKey));
     }
+
+    @Test
+    public void encryptAndSignWithNonSigningKeyFails() {
+        assertThrows(SOPGPException.KeyCannotSign.class, () -> sop.encrypt().signWith(nonSigningKey));
+    }
 }