diff --git a/src/include_diagram/model/diagram.cc b/src/include_diagram/model/diagram.cc
index 77513703..5f1bcf7d 100644
--- a/src/include_diagram/model/diagram.cc
+++ b/src/include_diagram/model/diagram.cc
@@ -61,7 +61,19 @@ std::string diagram::to_alias(const std::string &full_name) const
 {
     LOG_DBG("Looking for alias for {}", full_name);
 
-    return full_name;
+    auto path = common::model::filesystem_path{full_name};
+
+    if (path.is_empty())
+        throw error::uml_alias_missing(
+            fmt::format("Missing alias for '{}'", path.to_string()));
+
+    auto source_file = get_element<common::model::source_file>(path);
+
+    if (!source_file)
+        throw error::uml_alias_missing(
+            fmt::format("Missing alias for '{}'", path.to_string()));
+
+    return source_file.value().alias();
 }
 
 }
diff --git a/tests/t40001/.clang-uml b/tests/t40001/.clang-uml
index 6d55f301..660a1e13 100644
--- a/tests/t40001/.clang-uml
+++ b/tests/t40001/.clang-uml
@@ -16,4 +16,7 @@ diagrams:
         - ../../tests/t40001
     plantuml:
       before:
-        - "' t40001 test include diagram"
\ No newline at end of file
+        - "' t40001 test include diagram"
+      after:
+        - 'note right of {{ alias("include/lib1") }}: This is a lib1 include dir'
+        - 'note right of {{ alias("include/t40001_include1.h") }}: This is a t40001_include1.h include file'
\ No newline at end of file