diff --git a/Sources/JExtractSwift/TranslatedType.swift b/Sources/JExtractSwift/TranslatedType.swift
index 367c92cc..ca1ecf73 100644
--- a/Sources/JExtractSwift/TranslatedType.swift
+++ b/Sources/JExtractSwift/TranslatedType.swift
@@ -55,7 +55,12 @@ extension Swift2JavaVisitor {
       // Translate the generic arguments to the C-compatible types.
       let genericArgs = try memberType.genericArgumentClause.map { genericArgumentClause in
         try genericArgumentClause.arguments.map { argument in
-          try cCompatibleType(for: argument.argument)
+          switch argument.argument {
+          case .type(let argumentType):
+            try cCompatibleType(for: argumentType)
+          @unknown default:
+            throw TypeTranslationError.unimplementedType(TypeSyntax(memberType))
+          }
         }
       }
 
@@ -71,7 +76,12 @@ extension Swift2JavaVisitor {
       // Translate the generic arguments to the C-compatible types.
       let genericArgs = try identifierType.genericArgumentClause.map { genericArgumentClause in
         try genericArgumentClause.arguments.map { argument in
-          try cCompatibleType(for: argument.argument)
+          switch argument.argument {
+          case .type(let argumentType):
+            try cCompatibleType(for: argumentType)
+          @unknown default:
+            throw TypeTranslationError.unimplementedType(TypeSyntax(identifierType))
+          }
         }
       }