diff --git a/src/Language/PHP/Assignment.hs b/src/Language/PHP/Assignment.hs
index 23476874a..5d5ee32c3 100644
--- a/src/Language/PHP/Assignment.hs
+++ b/src/Language/PHP/Assignment.hs
@@ -99,6 +99,8 @@ type Syntax = '[
   , Declaration.Method
   , Syntax.PropertyModifier
   , Syntax.PropertyDeclaration
+  , Syntax.InterfaceBaseClause
+  , Syntax.InterfaceDeclaration
   , [] ]
 
 type Term = Term.Term (Data.Union.Union Syntax) (Record Location)
@@ -136,7 +138,7 @@ statement = handleError everything
   -- , constDeclaration
   -- , functionDefinition
   -- , classDeclaration
-  -- , interfaceDeclaration
+      , interfaceDeclaration
       , traitDeclaration
       , namespaceDefinition
       , namespaceUseDeclaration
@@ -456,6 +458,15 @@ castExpression = makeTerm <$> symbol CastExpression <*> children (flip Expressio
 castType :: Assignment
 castType = makeTerm <$> symbol CastType <*> (Syntax.CastType <$> source)
 
+interfaceDeclaration :: Assignment
+interfaceDeclaration = makeTerm <$> symbol InterfaceDeclaration <*> children (Syntax.InterfaceDeclaration <$> name <*> (interfaceBaseClause <|> emptyTerm) <*> manyTerm interfaceMemberDeclaration)
+
+interfaceBaseClause :: Assignment
+interfaceBaseClause = makeTerm <$> symbol InterfaceBaseClause <*> children (Syntax.InterfaceBaseClause <$> someTerm qualifiedName)
+
+interfaceMemberDeclaration :: Assignment
+interfaceMemberDeclaration = classConstDeclaration <|> methodDeclaration
+
 traitDeclaration :: Assignment
 traitDeclaration = makeTerm <$> symbol TraitDeclaration <*> children (Syntax.TraitDeclaration <$> name <*> manyTerm traitMemberDeclaration)
 
diff --git a/src/Language/PHP/Syntax.hs b/src/Language/PHP/Syntax.hs
index 52ee9661a..26865bf68 100644
--- a/src/Language/PHP/Syntax.hs
+++ b/src/Language/PHP/Syntax.hs
@@ -347,3 +347,17 @@ data PropertyModifier a = PropertyModifier a a
 instance Eq1 PropertyModifier where liftEq = genericLiftEq
 instance Ord1 PropertyModifier where liftCompare = genericLiftCompare
 instance Show1 PropertyModifier where liftShowsPrec = genericLiftShowsPrec
+
+data InterfaceDeclaration a = InterfaceDeclaration a a [a]
+  deriving (Diffable, Eq, Foldable, Functor, GAlign, Generic1, Mergeable, Ord, Show, Traversable)
+
+instance Eq1 InterfaceDeclaration where liftEq = genericLiftEq
+instance Ord1 InterfaceDeclaration where liftCompare = genericLiftCompare
+instance Show1 InterfaceDeclaration where liftShowsPrec = genericLiftShowsPrec
+
+newtype InterfaceBaseClause a = InterfaceBaseClause [a]
+  deriving (Diffable, Eq, Foldable, Functor, GAlign, Generic1, Mergeable, Ord, Show, Traversable)
+
+instance Eq1 InterfaceBaseClause where liftEq = genericLiftEq
+instance Ord1 InterfaceBaseClause where liftCompare = genericLiftCompare
+instance Show1 InterfaceBaseClause where liftShowsPrec = genericLiftShowsPrec