diff --git a/ssa/package.go b/ssa/package.go
index 12bc7df4..5410a302 100644
--- a/ssa/package.go
+++ b/ssa/package.go
@@ -110,6 +110,9 @@ type aProgram struct {
 	voidType  llvm.Type
 	voidPtrTy llvm.Type
 
+	rtIfaceTy llvm.Type
+	rtSliceTy llvm.Type
+
 	anyTy  Type
 	voidTy Type
 	boolTy Type
@@ -144,10 +147,28 @@ func (p Program) runtime() *types.Scope {
 	return p.rt
 }
 
-func (p Program) rtType(name string) *types.Named {
+func (p Program) rtNamed(name string) *types.Named {
 	return p.runtime().Lookup(name).Type().(*types.Named)
 }
 
+func (p Program) rtType(name string) Type {
+	return p.Type(p.rtNamed(name))
+}
+
+func (p Program) rtIface() llvm.Type {
+	if p.rtIfaceTy.IsNil() {
+		p.rtIfaceTy = p.rtType("Interface").ll
+	}
+	return p.rtIfaceTy
+}
+
+func (p Program) rtSlice() llvm.Type {
+	if p.rtSliceTy.IsNil() {
+		p.rtSliceTy = p.rtType("Slice").ll
+	}
+	return p.rtSliceTy
+}
+
 // NewPackage creates a new package.
 func (p Program) NewPackage(name, pkgPath string) Package {
 	mod := p.ctx.NewModule(pkgPath)
diff --git a/ssa/type.go b/ssa/type.go
index 6e5030f4..90978212 100644
--- a/ssa/type.go
+++ b/ssa/type.go
@@ -242,9 +242,9 @@ func (p Program) toLLVMType(typ types.Type) Type {
 		elem := p.Type(t.Elem())
 		return &aType{llvm.PointerType(elem.ll, 0), typ, vkInvalid}
 	case *types.Interface:
-		return p.toLLVMNamed(p.rtType("Interface"))
+		return &aType{p.rtIface(), typ, vkInvalid}
 	case *types.Slice:
-		return p.toLLVMNamed(p.rtType("Slice"))
+		return &aType{p.rtSlice(), typ, vkInvalid}
 	case *types.Map:
 	case *types.Struct:
 		return p.toLLVMStruct(t)