diff --git a/hc/api/decorators.py b/hc/api/decorators.py
index ae2bc8bb..cc0777e6 100644
--- a/hc/api/decorators.py
+++ b/hc/api/decorators.py
@@ -4,7 +4,7 @@ from functools import wraps
 
 from django.contrib.auth.models import User
 from django.http import HttpResponseBadRequest, JsonResponse
-from six import string_types
+from hc.lib.jsonschema import ValidationError, validate
 
 
 def uuid_or_400(f):
@@ -61,21 +61,10 @@ def validate_json(schema):
     def decorator(f):
         @wraps(f)
         def wrapper(request, *args, **kwds):
-            for key, spec in schema["properties"].items():
-                if key not in request.json:
-                    continue
-
-                value = request.json[key]
-                if spec["type"] == "string":
-                    if not isinstance(value, string_types):
-                        return make_error("%s is not a string" % key)
-                elif spec["type"] == "number":
-                    if not isinstance(value, int):
-                        return make_error("%s is not a number" % key)
-                    if "minimum" in spec and value < spec["minimum"]:
-                        return make_error("%s is too small" % key)
-                    if "maximum" in spec and value > spec["maximum"]:
-                        return make_error("%s is too large" % key)
+            try:
+                validate(request.json, schema)
+            except ValidationError as e:
+                return make_error("json validation error: %s" % e)
 
             return f(request, *args, **kwds)
         return wrapper
diff --git a/hc/lib/jsonschema.py b/hc/lib/jsonschema.py
new file mode 100644
index 00000000..1e5842a4
--- /dev/null
+++ b/hc/lib/jsonschema.py
@@ -0,0 +1,44 @@
+""" A minimal jsonschema validator.
+
+Supports only a tiny subset of jsonschema.
+
+"""
+
+from six import string_types
+
+
+class ValidationError(Exception):
+    pass
+
+
+def validate(obj, schema, obj_name="value"):
+    if schema.get("type") == "string":
+        if not isinstance(obj, string_types):
+            raise ValidationError("%s is not a string" % obj_name)
+
+    elif schema.get("type") == "number":
+        if not isinstance(obj, int):
+            raise ValidationError("%s is not a number" % obj_name)
+        if "minimum" in schema and obj < schema["minimum"]:
+            raise ValidationError("%s is too small" % obj_name)
+        if "maximum" in schema and obj > schema["maximum"]:
+            raise ValidationError("%s is too large" % obj_name)
+
+    elif schema.get("type") == "array":
+        if not isinstance(obj, list):
+            raise ValidationError("%s is not an array" % obj_name)
+
+        for v in obj:
+            validate(v, schema["items"], "an item in '%s'" % obj_name)
+
+    elif schema.get("type") == "object":
+        if not isinstance(obj, dict):
+            raise ValidationError("%s is not an object" % obj_name)
+
+        for key, spec in schema["properties"].items():
+            if key in obj:
+                validate(obj[key], spec, obj_name=key)
+
+    if "enum" in schema:
+        if obj not in schema["enum"]:
+            raise ValidationError("%s has unexpected value" % obj_name)
diff --git a/hc/lib/tests/test_jsonschema.py b/hc/lib/tests/test_jsonschema.py
new file mode 100644
index 00000000..65e10b5f
--- /dev/null
+++ b/hc/lib/tests/test_jsonschema.py
@@ -0,0 +1,76 @@
+from django.test import TestCase
+
+from hc.lib.jsonschema import ValidationError, validate
+
+
+class JsonSchemaTestCase(TestCase):
+
+    def test_it_validates_strings(self):
+        validate("foo", {"type": "string"})
+
+    def test_it_checks_string_type(self):
+        with self.assertRaises(ValidationError):
+            validate(123, {"type": "string"})
+
+    def test_it_validates_numbers(self):
+        validate(123, {"type": "number", "minimum": 0, "maximum": 1000})
+
+    def test_it_checks_int_type(self):
+        with self.assertRaises(ValidationError):
+            validate("foo", {"type": "number"})
+
+    def test_it_checks_min_value(self):
+        with self.assertRaises(ValidationError):
+            validate(5, {"type": "number", "minimum": 10})
+
+    def test_it_checks_max_value(self):
+        with self.assertRaises(ValidationError):
+            validate(5, {"type": "number", "maximum": 0})
+
+    def test_it_validates_objects(self):
+        validate({"foo": "bar"}, {
+            "type": "object",
+            "properties": {
+                "foo": {"type": "string"}
+            }
+        })
+
+    def test_it_checks_dict_type(self):
+        with self.assertRaises(ValidationError):
+            validate("not-object", {"type": "object"})
+
+    def test_it_validates_objects_properties(self):
+        with self.assertRaises(ValidationError):
+            validate({"foo": "bar"}, {
+                "type": "object",
+                "properties": {
+                    "foo": {"type": "number"}
+                }
+            })
+
+    def test_it_validates_arrays(self):
+        validate(["foo", "bar"], {
+            "type": "array",
+            "items": {"type": "string"}
+        })
+
+    def test_it_validates_array_type(self):
+        with self.assertRaises(ValidationError):
+            validate("not-an-array", {
+                "type": "array",
+                "items": {"type": "string"}
+            })
+
+    def test_it_validates_array_elements(self):
+        with self.assertRaises(ValidationError):
+            validate(["foo", "bar"], {
+                "type": "array",
+                "items": {"type": "number"}
+            })
+
+    def test_it_validates_enum(self):
+        validate("foo", {"enum": ["foo", "bar"]})
+
+    def test_it_rejects_a_value_not_in_enum(self):
+        with self.assertRaises(ValidationError):
+            validate("baz", {"enum": ["foo", "bar"]})