diff --git a/src/common/clang_utils.cc b/src/common/clang_utils.cc
index f2fce146..38881b9e 100644
--- a/src/common/clang_utils.cc
+++ b/src/common/clang_utils.cc
@@ -150,7 +150,13 @@ std::string to_string(const clang::QualType &type, const clang::ASTContext &ctx,
         result = "(anonymous)";
     else if (util::contains(result, "unnamed struct") ||
         util::contains(result, "unnamed union")) {
-        result = common::get_tag_name(*type->getAsTagDecl());
+        auto declarationTag = type->getAsTagDecl();
+        if (declarationTag == NULL) {
+            result = "(unnamed undeclared)";
+        }
+        else {
+            result = common::get_tag_name(*declarationTag);
+        }
     }
     else if (util::contains(result, "anonymous struct") ||
         util::contains(result, "anonymous union")) {