diff --git a/jsign-crypto/src/main/java/net/jsign/jca/JsignJcaProvider.java b/jsign-crypto/src/main/java/net/jsign/jca/JsignJcaProvider.java
index 95b5280a..aa74627d 100644
--- a/jsign-crypto/src/main/java/net/jsign/jca/JsignJcaProvider.java
+++ b/jsign-crypto/src/main/java/net/jsign/jca/JsignJcaProvider.java
@@ -201,7 +201,12 @@ protected void engineInitSign(PrivateKey privateKey) throws InvalidKeyException
             JsignJcaPrivateKey key = (JsignJcaPrivateKey) privateKey;
 
             try {
-                signature = Signature.getInstance(signingAlgorithm, key.getProvider());
+                Provider provider = key.getProvider();
+                if (provider == null) {
+                    signature = Signature.getInstance(signingAlgorithm);
+                } else {
+                    signature = Signature.getInstance(signingAlgorithm, provider);
+                }
             } catch (NoSuchAlgorithmException e) {
                 throw new RuntimeException(e);
             }