diff --git a/httpsig.py b/httpsig.py
index 067c2ed25..c2b777c6c 100644
--- a/httpsig.py
+++ b/httpsig.py
@@ -309,6 +309,8 @@ def create_signed_header(date_str: str, private_key_pem: str, nickname: str,
                               to_domain, to_port,
                               path, http_prefix, message_body_json_str,
                               content_type, algorithm, digest_algorithm)
+    if not signature_header:
+        return {}
     headers['signature'] = signature_header
     return headers
 
diff --git a/posts.py b/posts.py
index b5b1e592a..0fd78d693 100644
--- a/posts.py
+++ b/posts.py
@@ -2516,11 +2516,15 @@ def send_post(signing_priv_key_pem: str, project_version: str,
                              to_domain, to_port,
                              post_path, http_prefix, with_digest,
                              post_json_str, 'application/activity+json')
+    if not signature_header_json:
+        return 8
     signature_header_json_ld = \
         create_signed_header(None, private_key_pem, nickname, domain, port,
                              to_domain, to_port,
                              post_path, http_prefix, with_digest,
                              post_json_str, 'application/ld+json')
+    if not signature_header_json_ld:
+        return 9
 
     # if the "to" domain is within the shared items
     # federation list then send the token for this domain
@@ -2945,12 +2949,16 @@ def send_signed_json(post_json_object: {}, session, base_dir: str,
                              post_path, http_prefix, with_digest,
                              post_json_str,
                              'application/activity+json')
+    if not signature_header_json:
+        return 10
     signature_header_json_ld = \
         create_signed_header(None, private_key_pem, nickname, domain, port,
                              to_domain, to_port,
                              post_path, http_prefix, with_digest,
                              post_json_str,
                              'application/ld+json')
+    if not signature_header_json_ld:
+        return 11
     # optionally add a token so that the receiving instance may access
     # your shared items catalog
     if shared_items_token:
diff --git a/session.py b/session.py
index 78998fe35..9f0557fb9 100644
--- a/session.py
+++ b/session.py
@@ -200,6 +200,8 @@ def _get_json_signed(session, url: str, domain_full: str, session_headers: {},
         create_signed_header(None, signing_priv_key_pem, 'actor', domain, port,
                              to_domain, to_port, path, http_prefix,
                              with_digest, message_str, content_type)
+    if not signature_header_json:
+        return {}
     if debug:
         print('Signed GET signature_header_json ' + str(signature_header_json))
     # update the session headers from the signature headers
diff --git a/tests.py b/tests.py
index 86bc6501b..af0d0c3f9 100644
--- a/tests.py
+++ b/tests.py
@@ -316,6 +316,7 @@ def _test_http_signed_get(base_dir: str):
                              host_domain, port,
                              boxpath, http_prefix, False,
                              None, accept)
+    assert signature_header
 
     headers['signature'] = signature_header['signature']
     getreq_method = not with_digest
@@ -520,6 +521,8 @@ def _test_http_sig_new(algorithm: str, digest_algorithm: str):
                               domain, port,
                               path_str, http_prefix, message_body_json_str,
                               algorithm, digest_algorithm, debug)
+    assert signature_index_header
+    assert signature_header
     print('signature_index_header1: ' + str(signature_index_header))
     print('signature_header1: ' + str(signature_header))
     sig_input = "keyId=\"https://example.com/users/foo#main-key\"; " + \
@@ -623,6 +626,7 @@ def _test_httpsig_base(with_digest: bool, base_dir: str):
                               boxpath, http_prefix, message_body_json_str,
                               content_type, algorithm, digest_algorithm)
 
+    assert signature_header
     headers['signature'] = signature_header
     getreq_method = not with_digest
     debug = True
@@ -6929,6 +6933,8 @@ def _test_httpsig_base_new(with_digest: bool, base_dir: str,
                                   boxpath, http_prefix, message_body_json_str,
                                   algorithm, digest_algorithm, debug)
 
+    assert signature_index_header
+    assert signature_header
     headers['signature'] = signature_header
     headers['signature-input'] = signature_index_header
     print('headers: ' + str(headers))