diff --git a/lti/keys.py b/lti/keys.py
index d291a783..ffb1dda4 100644
--- a/lti/keys.py
+++ b/lti/keys.py
@@ -4,13 +4,20 @@ LTI Key Management for MediaCMS
 Manages RSA keys for signing Deep Linking responses (stored in database)
 """
 
+from jwcrypto import jwk
+
 
 def load_private_key():
-    """Load private key from database"""
+    """Load private key from database and convert to PEM format for PyJWT"""
     from .models import LTIToolKeys
 
     key_obj = LTIToolKeys.get_or_create_keys()
-    return key_obj.private_key_jwk
+
+    # Convert JWK dict to PEM string (PyJWT needs PEM format)
+    jwk_obj = jwk.JWK(**key_obj.private_key_jwk)
+    pem_bytes = jwk_obj.export_to_pem(private_key=True, password=None)
+
+    return pem_bytes.decode('utf-8')
 
 
 def load_public_key():