diff --git a/example.w b/example.w
index 51b8942..c329c6b 100644
--- a/example.w
+++ b/example.w
@@ -1,6 +1,16 @@
+interface Increments
+{
+    Increment(): void;
+}
+
 struct YourStruct
 {
     yourInt: int;
+
+    IncrementOther<T: Increments>(other: T): void
+    {
+        other.Increment();
+    }
 }
 
 struct MyStruct
diff --git a/generators/wraith.lex b/generators/wraith.lex
index f288c6e..1cf6fa9 100644
--- a/generators/wraith.lex
+++ b/generators/wraith.lex
@@ -13,6 +13,7 @@
 "string"                    return STRING;
 "bool"                      return BOOL;
 "struct"                    return STRUCT;
+"interface"                 return INTERFACE;
 "return"                    return RETURN;
 "static"                    return STATIC;
 "Reference"                 return REFERENCE;
diff --git a/generators/wraith.y b/generators/wraith.y
index 7aaf70a..69a4a9b 100644
--- a/generators/wraith.y
+++ b/generators/wraith.y
@@ -26,6 +26,7 @@ extern FILE *yyin;
 %token STRING
 %token BOOL
 %token STRUCT
+%token INTERFACE
 %token RETURN
 %token STATIC
 %token REFERENCE
@@ -307,14 +308,40 @@ Body                    : LEFT_BRACE Statements RIGHT_BRACE
                             $$ = $2;
                         }
 
-FunctionSignature       : Identifier LEFT_PAREN SignatureArguments RIGHT_PAREN COLON Type
+GenericConstraint       : Identifier COLON Identifier
                         {
-                            $$ = MakeFunctionSignatureNode($1, $6, $3, MakeFunctionModifiersNode(NULL, 0));
+                            $$ = MakeGenericConstraintNode($1, $3);
+                        }
+
+GenericConstraints      : GenericConstraint
+                        {
+                            $$ = StartGenericConstraintsNode($1);
+                        }
+                        | GenericConstraints COMMA GenericConstraint
+                        {
+                            $$ = AddGenericConstraint($1, $3);
+                        }
+                        ;
+
+GenericConstraintClause : LESS_THAN GenericConstraints GREATER_THAN
+                        {
+                            $$ = $2;
+                        }
+                        |
+                        {
+                            $$ = MakeEmptyGenericConstraintsNode();
+                        }
+                        ;
+
+/* FIXME: modifiers should be recursive */
+FunctionSignature       : Identifier GenericConstraintClause LEFT_PAREN SignatureArguments RIGHT_PAREN COLON Type
+                        {
+                            $$ = MakeFunctionSignatureNode($1, $7, $4, MakeFunctionModifiersNode(NULL, 0), $2);
                         }
                         | STATIC Identifier LEFT_PAREN SignatureArguments RIGHT_PAREN COLON Type
                         {
                             Node *modifier = MakeStaticNode();
-                            $$ = MakeFunctionSignatureNode($2, $7, $4, MakeFunctionModifiersNode(&modifier, 1));
+                            $$ = MakeFunctionSignatureNode($2, $7, $4, MakeFunctionModifiersNode(&modifier, 1), MakeEmptyGenericConstraintsNode());
                         }
 
 FunctionDeclaration     : FunctionSignature Body
@@ -327,6 +354,24 @@ StructDeclaration       : STRUCT Identifier LEFT_BRACE Declarations RIGHT_BRACE
                             $$ = MakeStructDeclarationNode($2, $4);
                         }
 
+InterfaceDeclaration    : INTERFACE Identifier LEFT_BRACE InterfaceChildren RIGHT_BRACE
+                        {
+                            $$ = MakeInterfaceDeclarationNode($2, $4);
+                        }
+
+InterfaceChild          : FunctionSignature SEMICOLON
+                        ;
+
+InterfaceChildren       : InterfaceChild
+                        {
+                            $$ = StartDeclarationSequenceNode($1);
+                        }
+                        | InterfaceChildren InterfaceChild
+                        {
+                            $$ = AddDeclarationNode($1, $2);
+                        }
+                        ;
+
 Declaration             : FunctionDeclaration
                         | VariableDeclaration SEMICOLON
                         ;
@@ -340,7 +385,9 @@ Declarations            : Declaration
                             $$ = AddDeclarationNode($1, $2);
                         }
 
-TopLevelDeclaration     : StructDeclaration;
+TopLevelDeclaration     : StructDeclaration
+                        | InterfaceDeclaration
+                        ;
 
 TopLevelDeclarations    : TopLevelDeclaration
                         {
diff --git a/src/ast.c b/src/ast.c
index 4f33a63..28cd79f 100644
--- a/src/ast.c
+++ b/src/ast.c
@@ -286,20 +286,59 @@ Node *MakeEmptyFunctionSignatureArgumentsNode()
     return node;
 }
 
+Node* MakeGenericConstraintNode(Node *identifierNode, Node *interfaceNode)
+{
+    Node* node = (Node*) malloc(sizeof(Node));
+    node->syntaxKind = GenericConstraint;
+    node->childCount = 2;
+    node->children = (Node**) malloc(sizeof(Node*) * 2);
+    node->children[0] = identifierNode;
+    node->children[1] = interfaceNode;
+    return node;
+}
+
+Node* StartGenericConstraintsNode(Node *genericNode)
+{
+    Node* node = (Node*) malloc(sizeof(Node));
+    node->syntaxKind = GenericConstraints;
+    node->childCount = 1;
+    node->children = (Node**) malloc(sizeof(Node*));
+    node->children[0] = genericNode;
+    return node;
+}
+
+Node* AddGenericConstraint(Node *genericsNode, Node *genericNode)
+{
+    genericsNode->children = realloc(genericsNode->children, sizeof(Node*) * (genericsNode->childCount + 1));
+    genericsNode->children[genericsNode->childCount] = genericNode;
+    genericsNode->childCount += 1;
+    return genericsNode;
+}
+
+Node* MakeEmptyGenericConstraintsNode()
+{
+    Node* node = (Node*) malloc(sizeof(Node));
+    node->syntaxKind = GenericConstraints;
+    node->childCount = 0;
+    return node;
+}
+
 Node* MakeFunctionSignatureNode(
     Node *identifierNode,
     Node* typeNode,
     Node* arguments,
-    Node* modifiersNode
+    Node* modifiersNode,
+    Node* genericConstraintsNode
 ) {
     Node* node = (Node*) malloc(sizeof(Node));
     node->syntaxKind = FunctionSignature;
-    node->childCount = 4;
+    node->childCount = 5;
     node->children = (Node**) malloc(sizeof(Node*) * (node->childCount));
     node->children[0] = identifierNode;
     node->children[1] = typeNode;
     node->children[2] = arguments;
     node->children[3] = modifiersNode;
+    node->children[4] = genericConstraintsNode;
     return node;
 }
 
@@ -329,6 +368,19 @@ Node* MakeStructDeclarationNode(
     return node;
 }
 
+Node* MakeInterfaceDeclarationNode(
+    Node *identifierNode,
+    Node *declarationSequenceNode
+) {
+    Node* node = (Node*) malloc(sizeof(Node));
+    node->syntaxKind = InterfaceDeclaration;
+    node->childCount = 2;
+    node->children = (Node**) malloc(sizeof(Node*) * 2);
+    node->children[0] = identifierNode;
+    node->children[1] = declarationSequenceNode;
+    return node;
+}
+
 Node* StartDeclarationSequenceNode(
     Node *declarationNode
 ) {
diff --git a/src/ast.h b/src/ast.h
index 8e49ace..3ddbe7d 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -21,9 +21,12 @@ typedef enum
     FunctionModifiers,
     FunctionSignature,
     FunctionSignatureArguments,
+    GenericConstraint,
+    GenericConstraints,
     Identifier,
     IfStatement,
     IfElseStatement,
+    InterfaceDeclaration,
     Number,
     PrimitiveTypeNode,
     ReferenceTypeNode,
@@ -154,21 +157,36 @@ Node* AddFunctionSignatureArgumentNode(
     Node *argumentsNode,
     Node *argumentNode
 );
-Node *MakeEmptyFunctionSignatureArgumentsNode();
+Node* MakeEmptyFunctionSignatureArgumentsNode();
+Node* MakeGenericConstraintNode(
+    Node *identifierNode,
+    Node *interfaceNode
+);
+Node* StartGenericConstraintsNode(Node *genericNode);
+Node* AddGenericConstraint(
+    Node *genericsNode,
+    Node *genericNode
+);
+Node* MakeEmptyGenericConstraintsNode();
 Node* MakeFunctionSignatureNode(
     Node *identifierNode,
-    Node* typeNode,
-    Node* argumentsNode,
-    Node* modifiersNode
+    Node *typeNode,
+    Node *argumentsNode,
+    Node *modifiersNode,
+    Node *genericConstraintsNode
 );
 Node* MakeFunctionDeclarationNode(
-    Node* functionSignatureNode,
-    Node* functionBodyNode
+    Node *functionSignatureNode,
+    Node *functionBodyNode
 );
 Node* MakeStructDeclarationNode(
     Node *identifierNode,
     Node *declarationSequenceNode
 );
+Node* MakeInterfaceDeclarationNode(
+    Node *identifierNode,
+    Node *declarationSequenceNode
+);
 Node* StartDeclarationSequenceNode(
     Node *declarationNode
 );
diff --git a/src/codegen.c b/src/codegen.c
index 3e75d1b..b5e9bf6 100644
--- a/src/codegen.c
+++ b/src/codegen.c
@@ -984,6 +984,11 @@ static void CompileStruct(LLVMModuleRef module, LLVMContextRef context, Node *no
     PopScopeFrame(scope);
 }
 
+static void CompileInterface(LLVMModuleRef module, LLVMContextRef context, Node *node)
+{
+
+}
+
 static void Compile(LLVMModuleRef module, LLVMContextRef context, Node *node)
 {
     uint32_t i;
@@ -994,9 +999,13 @@ static void Compile(LLVMModuleRef module, LLVMContextRef context, Node *node)
         {
             CompileStruct(module, context, node->children[i]);
         }
+        else if (node->children[i]->syntaxKind == InterfaceDeclaration)
+        {
+            CompileInterface(module, context, node->children[i]);
+        }
         else
         {
-            fprintf(stderr, "top level declarations that are not structs are forbidden!\n");
+            fprintf(stderr, "Top-level declarations that are not structs or interfaces are forbidden!\n");
         }
     }
 }