diff --git a/src/ahriman/core/alpm/pacman_database.py b/src/ahriman/core/alpm/pacman_database.py
index 75355461..3886a8f5 100644
--- a/src/ahriman/core/alpm/pacman_database.py
+++ b/src/ahriman/core/alpm/pacman_database.py
@@ -138,8 +138,14 @@ class PacmanDatabase(SyncHttpClient):
 
         Args:
             force(bool): force database synchronization (same as ``pacman -Syy``)
+
+        Raises:
+            PacmanError: on operation error (invalid scheme or incomplete configuration)
         """
-        server = next(iter(self.database.servers))
+        try:
+            server = next(iter(self.database.servers))
+        except StopIteration:
+            raise PacmanError("No configured servers available for database") from None
         filename = f"{self.database.name}.files.tar.gz"
         url = f"{server}/{filename}"
 
diff --git a/src/ahriman/core/exceptions.py b/src/ahriman/core/exceptions.py
index 9972c8ad..6908e8fd 100644
--- a/src/ahriman/core/exceptions.py
+++ b/src/ahriman/core/exceptions.py
@@ -116,6 +116,19 @@ class GitRemoteError(RuntimeError):
         RuntimeError.__init__(self, "Git remote failed")
 
 
+class GPGError(RuntimeError):
+    """
+    PGP/GPG related exception
+    """
+
+    def __init__(self, details: str) -> None:
+        """
+        Args:
+            details(str): details of the exception
+        """
+        RuntimeError.__init__(self, f"GPG operation failed: {details}")
+
+
 class InitializeError(RuntimeError):
     """
     base service initialization exception
diff --git a/src/ahriman/core/sign/gpg.py b/src/ahriman/core/sign/gpg.py
index 865ab0de..70c8f413 100644
--- a/src/ahriman/core/sign/gpg.py
+++ b/src/ahriman/core/sign/gpg.py
@@ -20,7 +20,7 @@
 from pathlib import Path
 
 from ahriman.core.configuration import Configuration
-from ahriman.core.exceptions import BuildError
+from ahriman.core.exceptions import BuildError, GPGError
 from ahriman.core.http import SyncHttpClient
 from ahriman.core.utils import check_output
 from ahriman.models.sign_settings import SignSettings
@@ -147,12 +147,19 @@ class GPG(SyncHttpClient):
 
         Returns:
             str: full PGP key fingerprint
+
+        Raises:
+            GPGError: if key is in wrong format
         """
-        metadata = check_output("gpg", "--with-colons", "--fingerprint", key, logger=self.logger)
         # fingerprint line will be like
         # fpr:::::::::43A663569A07EE1E4ECC55CC7E3A4240CE3C45C2:
-        fingerprint = next(filter(lambda line: line[:3] == "fpr", metadata.splitlines()))
-        return fingerprint.split(":")[-2]
+        metadata = check_output("gpg", "--with-colons", "--fingerprint", key, logger=self.logger)
+
+        try:
+            fingerprint = next(filter(lambda line: line[:3] == "fpr", metadata.splitlines()))
+            return fingerprint.split(":")[-2]
+        except (IndexError, StopIteration):
+            raise GPGError(f"key {key} has invalid metadata") from None
 
     def key_import(self, server: str, key: str) -> None:
         """
diff --git a/src/ahriman/models/user.py b/src/ahriman/models/user.py
index cec95385..ddfd19fd 100644
--- a/src/ahriman/models/user.py
+++ b/src/ahriman/models/user.py
@@ -88,8 +88,12 @@ class User:
         """
         if not self.password:
             return None
-        algo = next(segment for segment in self.password.split("$") if segment)
-        return f"${algo}$"
+
+        try:
+            algo = next(segment for segment in self.password.split("$") if segment)
+            return f"${algo}$"
+        except StopIteration:
+            return None
 
     @staticmethod
     def generate_password(length: int) -> str:
diff --git a/tests/ahriman/core/alpm/test_pacman_database.py b/tests/ahriman/core/alpm/test_pacman_database.py
index 4dcc0d53..3ed9dc3e 100644
--- a/tests/ahriman/core/alpm/test_pacman_database.py
+++ b/tests/ahriman/core/alpm/test_pacman_database.py
@@ -183,6 +183,15 @@ def test_sync_files_local(pacman_database: PacmanDatabase, mocker: MockerFixture
     copy_mock.assert_called_once_with(Path("/var/core.files.tar.gz"), pytest.helpers.anyvar(int))
 
 
+def test_sync_files_no_servers(pacman_database: PacmanDatabase) -> None:
+    """
+    must raise PacmanError if no servers are configured
+    """
+    pacman_database.database.servers = []
+    with pytest.raises(PacmanError):
+        pacman_database.sync_files(force=False)
+
+
 def test_sync_files_unknown_source(pacman_database: PacmanDatabase) -> None:
     """
     must raise an exception in case if server scheme is unsupported
diff --git a/tests/ahriman/core/sign/test_gpg.py b/tests/ahriman/core/sign/test_gpg.py
index 5df4e8a0..b67c5372 100644
--- a/tests/ahriman/core/sign/test_gpg.py
+++ b/tests/ahriman/core/sign/test_gpg.py
@@ -5,6 +5,7 @@ from pathlib import Path
 from pytest_mock import MockerFixture
 
 from ahriman.core.configuration import Configuration
+from ahriman.core.exceptions import GPGError
 from ahriman.core.sign.gpg import GPG
 from ahriman.models.sign_settings import SignSettings
 
@@ -113,6 +114,15 @@ fpr:::::::::43A663569A07EE1E4ECC55CC7E3A4240CE3C45C2:""")
     check_output_mock.assert_called_once_with("gpg", "--with-colons", "--fingerprint", key, logger=gpg.logger)
 
 
+def test_key_fingerprint_invalid(gpg: GPG, mocker: MockerFixture) -> None:
+    """
+    must raise GPGError if no fingerprint found in output
+    """
+    mocker.patch("ahriman.core.sign.gpg.check_output", return_value="no fingerprint here")
+    with pytest.raises(GPGError):
+        gpg.key_fingerprint("0xCE3C45C2")
+
+
 def test_key_import(gpg: GPG, mocker: MockerFixture) -> None:
     """
     must import PGP key from the server
diff --git a/tests/ahriman/models/test_user.py b/tests/ahriman/models/test_user.py
index a04fdeef..0cb0c072 100644
--- a/tests/ahriman/models/test_user.py
+++ b/tests/ahriman/models/test_user.py
@@ -12,6 +12,8 @@ def test_algo() -> None:
     """
     assert User(username="user", password=None, access=UserAccess.Read).algo is None
     assert User(username="user", password="", access=UserAccess.Read).algo is None
+    assert User(username="user", password="$$$", access=UserAccess.Read).algo is None
+
     assert User(
         username="user",
         password="$6$rounds=656000$mWBiecMPrHAL1VgX$oU4Y5HH8HzlvMaxwkNEJjK13ozElyU1wAHBoO/WW5dAaE4YEfnB0X3FxbynKMl4FBdC3Ovap0jINz4LPkNADg0",