diff --git a/README.md b/README.md
index 84fdb9a..ff60519 100644
--- a/README.md
+++ b/README.md
@@ -32,7 +32,7 @@ graphql-tools = { version = "...", features = "graphql_parser_fork", default-fea
 
 #### Validation Rules
 
-> This comparison is based on `graphql-js` refernece implementation.
+> This comparison is based on `graphql-js` reference implementation.
 
 - [x] ExecutableDefinitions (not actually needed)
 - [x] UniqueOperationNames
diff --git a/src/ast/operation_visitor.rs b/src/ast/operation_visitor.rs
index 044e245..b9f6716 100644
--- a/src/ast/operation_visitor.rs
+++ b/src/ast/operation_visitor.rs
@@ -167,9 +167,43 @@ fn visit_definitions<'a, Visitor, UserContext>(
             Definition::Operation(operation) => match operation {
                 OperationDefinition::Query(_) => Some(&context.schema.query_type().name),
                 OperationDefinition::SelectionSet(_) => Some(&context.schema.query_type().name),
-                OperationDefinition::Mutation(_) => context.schema.mutation_type().map(|t| &t.name),
+                OperationDefinition::Mutation(_) => {
+                    context.schema.mutation_type().map(|t| &t.name).or_else(|| {
+                        // Awkward hack but enables me to move forward
+                        // Somehow the `mutation_type()` gives None, even though `Mutation` type is defined in the schema.
+                        if let Some(type_definition) = context.schema.type_by_name("Mutation") {
+                            return match type_definition {
+                                crate::parser::schema::TypeDefinition::Object(object_type) => {
+                                    Some(&object_type.name)
+                                }
+                                _ => None,
+                            };
+                        }
+
+                        None
+                    })
+                }
                 OperationDefinition::Subscription(_) => {
-                    context.schema.subscription_type().map(|t| &t.name)
+                    context
+                        .schema
+                        .subscription_type()
+                        .map(|t| &t.name)
+                        .or_else(|| {
+                            // Awkward hack but enables me to move forward
+                            // Somehow the `subscription_type()` gives None, even though `Subscription` type is defined in the schema.
+                            if let Some(type_definition) =
+                                context.schema.type_by_name("Subscription")
+                            {
+                                return match type_definition {
+                                    crate::parser::schema::TypeDefinition::Object(object_type) => {
+                                        Some(&object_type.name)
+                                    }
+                                    _ => None,
+                                };
+                            }
+
+                            None
+                        })
                 }
             },
         };
diff --git a/src/validation/rules/fields_on_correct_type.rs b/src/validation/rules/fields_on_correct_type.rs
index 89fe9b4..88c63df 100644
--- a/src/validation/rules/fields_on_correct_type.rs
+++ b/src/validation/rules/fields_on_correct_type.rs
@@ -118,6 +118,12 @@ pub static FIELDS_ON_CORRECT_TYPE_TEST_SCHEMA: &str = "
   type Query {
     human: Human
   }
+  type Mutation {
+    deletePetByName(name: String): Pet
+  }
+  type Subscription {
+    onNewPet: Pet
+  }
 ";
 
 #[test]
@@ -219,6 +225,69 @@ fn ignores_fields_on_unknown_type() {
     assert_eq!(get_messages(&errors).len(), 0);
 }
 
+#[test]
+fn unknown_query_field() {
+    use crate::validation::test_utils::*;
+
+    let mut plan = create_plan_from_rule(Box::new(FieldsOnCorrectType {}));
+    let errors = test_operation_with_schema(
+        "query test {
+          unknownField
+        }",
+        &FIELDS_ON_CORRECT_TYPE_TEST_SCHEMA,
+        &mut plan,
+    );
+
+    let messages = get_messages(&errors);
+    assert_eq!(messages.len(), 1);
+    assert_eq!(
+        messages,
+        vec!["Cannot query field \"unknownField\" on type \"Query\"."]
+    );
+}
+
+#[test]
+fn unknown_mutation_field() {
+    use crate::validation::test_utils::*;
+
+    let mut plan = create_plan_from_rule(Box::new(FieldsOnCorrectType {}));
+    let errors = test_operation_with_schema(
+        "mutation test {
+          unknownField
+        }",
+        &FIELDS_ON_CORRECT_TYPE_TEST_SCHEMA,
+        &mut plan,
+    );
+
+    let messages = get_messages(&errors);
+    assert_eq!(messages.len(), 1);
+    assert_eq!(
+        messages,
+        vec!["Cannot query field \"unknownField\" on type \"Mutation\"."]
+    );
+}
+
+#[test]
+fn unknown_subscription_field() {
+    use crate::validation::test_utils::*;
+
+    let mut plan = create_plan_from_rule(Box::new(FieldsOnCorrectType {}));
+    let errors = test_operation_with_schema(
+        "subscription test {
+          unknownField
+        }",
+        &FIELDS_ON_CORRECT_TYPE_TEST_SCHEMA,
+        &mut plan,
+    );
+
+    let messages = get_messages(&errors);
+    assert_eq!(messages.len(), 1);
+    assert_eq!(
+        messages,
+        vec!["Cannot query field \"unknownField\" on type \"Subscription\"."]
+    );
+}
+
 #[test]
 fn reports_errors_when_type_is_known_again() {
     use crate::validation::test_utils::*;