diff --git a/cmd/libs/go2idl/go-to-protobuf/protobuf/namer.go b/cmd/libs/go2idl/go-to-protobuf/protobuf/namer.go
index 60060d4edf4..423577a12e9 100644
--- a/cmd/libs/go2idl/go-to-protobuf/protobuf/namer.go
+++ b/cmd/libs/go2idl/go-to-protobuf/protobuf/namer.go
@@ -157,6 +157,21 @@ func assignGoTypeToProtoPackage(p *protobufPackage, t *types.Type, local, global
 	}
 }
 
+// isTypeApplicableToProtobuf checks to see if a type is relevant for protobuf processing.
+// Currently, it filters out functions and private types.
+func isTypeApplicableToProtobuf(t *types.Type) bool {
+	// skip functions -- we don't care about them for protobuf
+	if t.Kind == types.Func || (t.Kind == types.DeclarationOf && t.Underlying.Kind == types.Func) {
+		return false
+	}
+	// skip private types
+	if namer.IsPrivateGoName(t.Name.Name) {
+		return false
+	}
+
+	return true
+}
+
 func (n *protobufNamer) AssignTypesToPackages(c *generator.Context) error {
 	global := make(typeNameSet)
 	for _, p := range n.packages {
@@ -167,6 +182,10 @@ func (n *protobufNamer) AssignTypesToPackages(c *generator.Context) error {
 			if t.Name.Package != p.PackagePath {
 				continue
 			}
+			if !isTypeApplicableToProtobuf(t) {
+				// skip types that we don't care about, like functions
+				continue
+			}
 			assignGoTypeToProtoPackage(p, t, local, global, optional)
 		}
 		p.FilterTypes = make(map[types.Name]struct{})