diff --git a/spec/Section 3 -- Type System.md b/spec/Section 3 -- Type System.md
index 8940956f7..f4cfa9746 100644
--- a/spec/Section 3 -- Type System.md	
+++ b/spec/Section 3 -- Type System.md	
@@ -96,6 +96,9 @@ type Query {
 }
 ```
 
+Note: A `query` root operation type which does not define any fields still
+allows for [Schema Introspection](#sec-Schema-Introspection).
+
 Similarly, the following mutation is valid if a `mutation` root operation type
 has a field named "setName". Note that the `query` and `mutation` root types
 must be different types.
@@ -792,8 +795,7 @@ Objects are never valid inputs.
 Object types have the potential to be invalid if incorrectly defined. This set
 of rules must be adhered to by every Object type in a GraphQL schema.
 
-1. An Object type must define one or more fields.
-2. For each field of an Object type:
+1. For each field of an Object type:
    1. The field must have a unique name within that Object type;
       no two fields may share the same name.
    2. The field must not have a name which begins with the
@@ -804,8 +806,8 @@ of rules must be adhered to by every Object type in a GraphQL schema.
          characters {"__"} (two underscores).
       2. The argument must accept a type where {IsInputType(argumentType)}
          returns {true}.
-4. An object type may declare that it implements one or more unique interfaces.
-5. An object type must be a super-set of all interfaces it implements:
+2. An object type may declare that it implements one or more unique interfaces.
+3. An object type must be a super-set of all interfaces it implements:
    1. The object type must include a field of the same name for every field
       defined in an interface.
       1. The object field must be of a type which is equal to or a sub-type of
@@ -1052,8 +1054,7 @@ Interfaces are never valid inputs.
 
 Interface types have the potential to be invalid if incorrectly defined.
 
-1. An Interface type must define one or more fields.
-2. For each field of an Interface type:
+1. For each field of an Interface type:
    1. The field must have a unique name within that Interface type;
       no two fields may share the same name.
    2. The field must not have a name which begins with the
@@ -1402,16 +1403,17 @@ Literal Value            | Variables               | Coerced Value
 `$var`                   | `{ var: "abc123" } }`   | Error: Incorrect value
 `{ a: "abc", b: "123" }` | `{}`                    | Error: Incorrect value for field {b}
 `{ a: "abc" }`           | `{}`                    | Error: Missing required field {b}
-`{ b: $var }`            | `{}`                    | Error: Missing required field {b}.
+`{ b: $var }`            | `{}`                    | Error: Missing required field {b}
+`{ }`                    | `{}`                    | Error: Missing required field {b}
 `$var`                   | `{ var: { a: "abc" } }` | Error: Missing required field {b}
+`$var`                   | `{ var: { } }`          | Error: Missing required field {b}
 `{ a: "abc", b: null }`  | `{}`                    | Error: {b} must be non-null.
 `{ b: $var }`            | `{ var: null }`         | Error: {b} must be non-null.
 `{ b: 123, c: "xyz" }`   | `{}`                    | Error: Unexpected field {c}
 
 **Type Validation**
 
-1. An Input Object type must define one or more input fields.
-2. For each input field of an Input Object type:
+1. For each input field of an Input Object type:
    1. The input field must have a unique name within that Input Object type;
       no two input fields may share the same name.
    2. The input field must not have a name which begins with the
diff --git a/spec/Section 4 -- Introspection.md b/spec/Section 4 -- Introspection.md
index 9418a3b7c..c7e6eb446 100644
--- a/spec/Section 4 -- Introspection.md	
+++ b/spec/Section 4 -- Introspection.md	
@@ -98,6 +98,8 @@ identify which actual type of the possible types has been returned.
 
 This field is implicit and does not appear in the fields list in any defined type.
 
+Note: The `__typename` field can always be queried, even if an Object or Interface does not define any fields.
+
 
 ## Schema Introspection