diff --git a/src/Language/GraphQL/AST/Document.hs b/src/Language/GraphQL/AST/Document.hs
index 101cf78..11317d8 100644
--- a/src/Language/GraphQL/AST/Document.hs
+++ b/src/Language/GraphQL/AST/Document.hs
@@ -482,12 +482,9 @@ instance Monoid Description
 data TypeDefinition
     = ScalarTypeDefinition Description Name [Directive]
     | ObjectTypeDefinition
-        Description
-        Name
-        (ImplementsInterfaces [])
-        [Directive]
-        [FieldDefinition]
-    | InterfaceTypeDefinition Description Name [Directive] [FieldDefinition]
+        Description Name (ImplementsInterfaces []) [Directive] [FieldDefinition]
+    | InterfaceTypeDefinition
+        Description Name (ImplementsInterfaces []) [Directive] [FieldDefinition]
     | UnionTypeDefinition Description Name [Directive] (UnionMemberTypes [])
     | EnumTypeDefinition Description Name [Directive] [EnumValueDefinition]
     | InputObjectTypeDefinition
diff --git a/src/Language/GraphQL/AST/Encoder.hs b/src/Language/GraphQL/AST/Encoder.hs
index a1076e4..603023b 100644
--- a/src/Language/GraphQL/AST/Encoder.hs
+++ b/src/Language/GraphQL/AST/Encoder.hs
@@ -226,10 +226,11 @@ typeDefinition formatter = \case
         <> optempty (directives formatter) directives'
         <> eitherFormat formatter " " ""
         <> bracesList formatter (fieldDefinition nextFormatter) fields'
-    Full.InterfaceTypeDefinition description' name' directives' fields'
+    Full.InterfaceTypeDefinition description' name' ifaces' directives' fields'
         -> optempty (description formatter) description'
         <> "interface "
         <> Lazy.Text.fromStrict name'
+        <> optempty (" " <>) (implementsInterfaces ifaces')
         <> optempty (directives formatter) directives'
         <> eitherFormat formatter " " ""
         <> bracesList formatter (fieldDefinition nextFormatter) fields'
diff --git a/src/Language/GraphQL/AST/Parser.hs b/src/Language/GraphQL/AST/Parser.hs
index f325ee7..d3a6b34 100644
--- a/src/Language/GraphQL/AST/Parser.hs
+++ b/src/Language/GraphQL/AST/Parser.hs
@@ -214,6 +214,7 @@ interfaceTypeDefinition :: Full.Description -> Parser Full.TypeDefinition
 interfaceTypeDefinition description' = Full.InterfaceTypeDefinition description'
     <$ symbol "interface"
     <*> name
+    <*> option (Full.ImplementsInterfaces []) (implementsInterfaces sepBy1)
     <*> directives
     <*> braces (many fieldDefinition)
     <?> "InterfaceTypeDefinition"
diff --git a/src/Language/GraphQL/Validate.hs b/src/Language/GraphQL/Validate.hs
index 5feb85a..1d24523 100644
--- a/src/Language/GraphQL/Validate.hs
+++ b/src/Language/GraphQL/Validate.hs
@@ -210,7 +210,7 @@ typeDefinition context rule = \case
     Full.ObjectTypeDefinition _ _ _ directives' fields
         -> directives context rule objectLocation directives'
         >< foldMap (fieldDefinition context rule) fields
-    Full.InterfaceTypeDefinition _ _ directives' fields
+    Full.InterfaceTypeDefinition _ _ _ directives' fields
         -> directives context rule interfaceLocation directives'
         >< foldMap (fieldDefinition context rule) fields
     Full.UnionTypeDefinition _ _ directives' _ ->
diff --git a/tests/Language/GraphQL/AST/EncoderSpec.hs b/tests/Language/GraphQL/AST/EncoderSpec.hs
index e98d5ef..82d059a 100644
--- a/tests/Language/GraphQL/AST/EncoderSpec.hs
+++ b/tests/Language/GraphQL/AST/EncoderSpec.hs
@@ -181,7 +181,7 @@ spec = do
                 argument = Full.InputValueDefinition mempty "arg" someType Nothing mempty
                 arguments = Full.ArgumentsDefinition [argument]
                 definition' = Full.TypeDefinition
-                    $ Full.InterfaceTypeDefinition mempty "UUID" mempty
+                    $ Full.InterfaceTypeDefinition mempty "UUID" (Full.ImplementsInterfaces []) mempty
                     $ pure
                     $ Full.FieldDefinition mempty "value" arguments someType mempty
                 expected = "interface UUID {\n\
diff --git a/tests/Language/GraphQL/AST/ParserSpec.hs b/tests/Language/GraphQL/AST/ParserSpec.hs
index 3bd2576..9f992bb 100644
--- a/tests/Language/GraphQL/AST/ParserSpec.hs
+++ b/tests/Language/GraphQL/AST/ParserSpec.hs
@@ -103,6 +103,12 @@ spec = describe "Parser" $ do
             \  name: String\n\
             \}"
 
+    it "parses ImplementsInterfaces on interfaces" $
+        parse document "" `shouldSucceedOn`
+            "interface Person implements NamedEntity & ValuedEntity {\n\
+            \  name: String\n\
+            \}"
+
     it "parses minimal enum type definition" $
         parse document "" `shouldSucceedOn`
             "enum Direction {\n\