diff --git a/yamale/schema/schema.py b/yamale/schema/schema.py
index 2b8af90..cee1f67 100644
--- a/yamale/schema/schema.py
+++ b/yamale/schema/schema.py
@@ -4,6 +4,12 @@
 from .. import validators as val
 
 
+class FatalValidationError(Exception):
+    def __init__(self, error):
+        super().__init__()
+        self.error = error
+
+
 class Schema(object):
     """
     Makes a Schema object from a schema dict.
@@ -45,7 +51,10 @@ def _parse_schema_item(self, path, expression, validators):
 
     def validate(self, data, data_name, strict):
         path = DataPath()
-        errors = self._validate(self._schema, data, path, strict)
+        try:
+            errors = self._validate(self._schema, data, path, strict)
+        except FatalValidationError as e:
+            errors = [e.error]
         return ValidationResult(data_name, self.name, errors)
 
     def _validate_item(self, validator, data, path, strict, key):
@@ -91,7 +100,6 @@ def _validate(self, validator, data, path, strict):
 
         if isinstance(validator, val.Include):
             errors += self._validate_include(validator, data, path, strict)
-
         elif isinstance(validator, (val.Map, val.List)):
             errors += self._validate_map_list(validator, data, path, strict)
 
@@ -146,7 +154,7 @@ def _validate_map_list(self, validator, data, path, strict):
     def _validate_include(self, validator, data, path, strict):
         include_schema = self.includes.get(validator.include_name)
         if not include_schema:
-            return [("Include '%s' has not been defined." % validator.include_name)]
+            raise FatalValidationError("Include '%s' has not been defined." % validator.include_name)
         strict = strict if validator.strict is None else validator.strict
         return include_schema._validate(include_schema._schema, data, path, strict)
 
diff --git a/yamale/tests/fixtures/any_undefined.yaml b/yamale/tests/fixtures/any_undefined.yaml
new file mode 100644
index 0000000..a3a3e61
--- /dev/null
+++ b/yamale/tests/fixtures/any_undefined.yaml
@@ -0,0 +1 @@
+thing: "a string :D"
diff --git a/yamale/tests/fixtures/any_undefined_schema.yaml b/yamale/tests/fixtures/any_undefined_schema.yaml
new file mode 100644
index 0000000..4407ff7
--- /dev/null
+++ b/yamale/tests/fixtures/any_undefined_schema.yaml
@@ -0,0 +1 @@
+thing: any(str(), include('Wtf'))
diff --git a/yamale/tests/test_functional.py b/yamale/tests/test_functional.py
index 97c8fd1..c78c8ad 100644
--- a/yamale/tests/test_functional.py
+++ b/yamale/tests/test_functional.py
@@ -20,6 +20,8 @@
 
 anys = {"schema": "any.yaml", "bad": "any_bad.yaml", "good": "any_good.yaml"}
 
+any_undefined = {"schema": "any_undefined_schema.yaml", "bad": "any_undefined.yaml"}
+
 list_include = {"schema": "list_include.yaml", "good": "list_include_good.yaml"}
 
 issue_22 = {"schema": "issue_22.yaml", "good": "issue_22_good.yaml"}
@@ -93,6 +95,7 @@
     lists,
     maps,
     anys,
+    any_undefined,
     list_include,
     issue_22,
     issue_50,
@@ -195,6 +198,10 @@ def test_bad_anys():
     assert count_exception_lines(anys["schema"], anys["bad"]) == 5
 
 
+def test_undefined_include():
+    assert count_exception_lines(any_undefined["schema"], any_undefined["bad"]) == 1
+
+
 def test_bad_regexes():
     assert count_exception_lines(regexes["schema"], regexes["bad"]) == 4