diff --git a/secret_loader/__init__.py b/secret_loader/__init__.py
index ec106cb..d00a31e 100644
--- a/secret_loader/__init__.py
+++ b/secret_loader/__init__.py
@@ -26,8 +26,6 @@ Secret loading order:
    usage; very unsuited for server environments. Requires `pass` installed
    locally, and configuration of the `PASS_STORE_SUBFOLDER` through one of the above
    methods.
-4. Vault instance if configured. Suited for production environments. **NOTE:
-   This is barely supported.** Requires `hvac` python package.
 
 ## Future extensions
 
@@ -54,11 +52,6 @@ import os
 import subprocess
 from pathlib import Path
 
-try:
-    import hvac
-except ImportError:
-    hvac = None
-
 from ._version import __version__
 
 __all__ = ['__version__', 'SecretLoader']
@@ -126,7 +119,7 @@ class SecretLoader:
                 msg = 'Prefix must be uppercase'
                 raise ValueError(msg)
             if self.env_key_prefix.endswith('_'):
-                msg = 'Prefix must not end with _ (this will be added automatically)'
+                msg = 'Prefix must not end with "_" (this will be added automatically)'
                 raise ValueError(msg)
 
         # Setup secrets path
@@ -139,21 +132,13 @@ class SecretLoader:
         # Setup pass
         self.pass_folder = self._load_or_none(ENV_KEY_PASS_FOLDER)
 
-        # Setup vault
-        if hvac:
-            self.vault_client = hvac.Client(
-                url=self._load_or_none(ENV_KEY_VAULT_URL),
-                token=self._load_or_none(ENV_KEY_VAULT_TOKEN),
-                vault_mount_point=self._load_or_none(ENV_KEY_VAULT_MOUNT_POINT),
-            )
-
     def load_or_fail(self, secret_name: str) -> str:
         """Load secret with the given key, from one of the backends or
         throw an exception if not found.
         """
         value = self._load_or_none(secret_name)
         if value is None:
-            raise Exception(self._format_error_message(secret_name))
+            raise ValueError(self._format_error_message(secret_name))
         logger.info('Loaded secret with key: %s', secret_name)
         return value
 
@@ -178,7 +163,6 @@ class SecretLoader:
             self.hardcoded.get(secret_name)
             or self._load_or_none_path_or_file(secret_name)
             or self._load_or_none_local_password_store(secret_name)
-            or self._load_or_none_vault(secret_name)
         )
 
     def _load_or_none_path_or_file(self, secret_name: str) -> str | None:
@@ -220,28 +204,19 @@ class SecretLoader:
             check=False,
             shell=False,
         )
-        if process.returncode:
-            return None
 
-        password_file = process.stdout.decode('utf8')
-        for line in password_file.split('\n'):
-            return line
-        return None
-
-    def _load_or_none_vault(self, secret_name: str) -> str | None:
-        """Load secret from the configured vault instance.
-
-        Returns `None` if vault instance is not configured, or if the value
-        instance does not know about the secret.
-        """
-        if self.vault_client is None:
-            return None
-
-        read_secret_result = self.vault_client.secrets.kv.v1.read_secret(
-            path=secret_name.lower(),
-            mount_point=self.vault_mount_point,
+        return self._convert_pass_process_result_to_password(
+            process.returncode, process.stdout
         )
-        return read_secret_result['data']['value']
+
+    def _convert_pass_process_result_to_password(
+        self, returncode: int, stdout: bytes
+    ) -> str | None:
+        if returncode != 0:
+            return None
+
+        password_file = stdout.decode('utf8')
+        return password_file.split('\n')[0]
 
     def _format_error_message(self, secret_name: str) -> str:
         """Formats an error message with solution suggestions for the given
diff --git a/test/test_init.py b/test/test_init.py
index 26adc23..d3f563f 100644
--- a/test/test_init.py
+++ b/test/test_init.py
@@ -1,4 +1,5 @@
 import secret_loader
+import pytest
 
 
 def test_hardcoded():
@@ -6,12 +7,52 @@ def test_hardcoded():
     assert loader.load('ENV_KEY_PREFIX') == 'TEST'
     assert loader.load('KEY') == 'VALUE'
 
+    assert loader.load_or_fail('ENV_KEY_PREFIX') == 'TEST'
+    assert loader.load_or_fail('KEY') == 'VALUE'
+
 
 def test_lookup_secrets_dir():
     loader = secret_loader.SecretLoader(SECRETS_DIRECTORY='test/example-secrets')
     assert loader.load('MY_SECRET') == 'HELLO SECRET'
+    assert loader.load_or_fail('MY_SECRET') == 'HELLO SECRET'
 
 
 def test_lookup_unknown():
     loader = secret_loader.SecretLoader()
     assert loader.load('UNKNOWN') is None
+
+
+def test_fail_hardcoded_prefix_lowercase():
+    with pytest.raises(ValueError, match='Prefix must be uppercase'):
+        secret_loader.SecretLoader(ENV_KEY_PREFIX='test')
+
+
+def test_fail_hardcoded_prefix_with_trailing_underscore():
+    with pytest.raises(
+        ValueError,
+        match=r'Prefix must not end with "_" \(this will be added automatically\)',
+    ):
+        secret_loader.SecretLoader(ENV_KEY_PREFIX='TEST_')
+
+
+def test_lookup_unknown_or_fail():
+    loader = secret_loader.SecretLoader(
+        ENV_KEY_PREFIX='TEST', PASS_STORE_SUBFOLDER='test'
+    )
+    with pytest.raises(
+        ValueError, match='Failed to load secret with key:.*UNKNOWN.*'
+    ) as e:
+        assert loader.load_or_fail('UNKNOWN')
+
+    assert 'Write secret to file' in str(e.value)
+    assert 'Add environment variable pointing to written secret' in str(e.value)
+    assert 'Write secret to password store entry' in str(e.value)
+
+
+def test_convert_process():
+    loader = secret_loader.SecretLoader()
+    assert loader._convert_pass_process_result_to_password(1, b'') is None
+    assert (
+        loader._convert_pass_process_result_to_password(0, b'Hello\nWorld') == 'Hello'
+    )
+    assert loader._convert_pass_process_result_to_password(0, b'') == ''