diff --git a/docs/references.rst b/docs/references.rst
index 2664e9b..9f24299 100644
--- a/docs/references.rst
+++ b/docs/references.rst
@@ -7,3 +7,7 @@ Resolving JSON References
 
 .. autoclass:: RefResolver
     :members:
+
+.. autoexception:: RefResolutionError
+
+    A JSON reference failed to resolve.
diff --git a/docs/validate.rst b/docs/validate.rst
index 4db45b4..48ee032 100644
--- a/docs/validate.rst
+++ b/docs/validate.rst
@@ -94,6 +94,7 @@ adhere to.
 
         :type type: str
         :rtype: bool
+        :raises: :exc:`UnknownType` if ``type`` is not a known type.
 
         The special type ``"any"`` is valid for any given instance.
 
diff --git a/jsonschema.py b/jsonschema.py
index bced6e1..6e8fe05 100644
--- a/jsonschema.py
+++ b/jsonschema.py
@@ -54,6 +54,23 @@ FLOAT_TOLERANCE = 10 ** -15
 validators = {}
 
 
+class _Error(Exception):
+    def __init__(self, message, validator=None, path=()):
+        super(_Error, self).__init__(message, validator, path)
+        self.message = message
+        self.path = list(path)
+        self.validator = validator
+
+    def __str__(self):
+        return self.message
+
+
+class SchemaError(_Error): pass
+class ValidationError(_Error): pass
+class RefResolutionError(Exception): pass
+class UnknownType(Exception): pass
+
+
 def validates(version):
     """
     Register the decorated validator for a ``version`` of the specification.
@@ -72,31 +89,6 @@ def validates(version):
     return _validates
 
 
-class UnknownType(Exception):
-    """
-    An attempt was made to check if an instance was of an unknown type.
-
-    """
-
-
-class RefResolutionError(Exception):
-    """
-    A JSON reference failed to resolve.
-
-    """
-
-
-class SchemaError(Exception):
-    def __init__(self, message, validator=None, path=()):
-        super(SchemaError, self).__init__(message, validator, path)
-        self.message = message
-        self.path = list(path)
-        self.validator = validator
-
-    def __str__(self):
-        return self.message
-
-
 class ValidationError(Exception):
     def __init__(self, message, validator=None, path=()):
         # Any validator that recurses (e.g. properties and items) must append