diff --git a/diagnostic_aggregator/CMakeLists.txt b/diagnostic_aggregator/CMakeLists.txt
index 2af6b867..87e74593 100644
--- a/diagnostic_aggregator/CMakeLists.txt
+++ b/diagnostic_aggregator/CMakeLists.txt
@@ -89,7 +89,8 @@ if(BUILD_TESTING)
     "primitive_analyzers"
     "all_analyzers"
     "analyzer_group"
-    "empty_root_path")
+    "empty_root_path"
+    "expected_only_analyzer")
 
   foreach(test_name ${create_analyzers_tests})
     file(TO_CMAKE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/test/${test_name}.yaml" PARAMETER_FILE)
diff --git a/diagnostic_aggregator/src/generic_analyzer.cpp b/diagnostic_aggregator/src/generic_analyzer.cpp
index 3965b226..580b6c4a 100644
--- a/diagnostic_aggregator/src/generic_analyzer.cpp
+++ b/diagnostic_aggregator/src/generic_analyzer.cpp
@@ -113,7 +113,8 @@ bool GenericAnalyzer::init(
       RCLCPP_DEBUG(
         rclcpp::get_logger("GenericAnalyzer"), "GenericAnalyzer '%s' found expected: %s",
         nice_name_.c_str(), pvalue.value_to_string().c_str());
-      for (auto exp : pvalue.as_string_array()) {
+      expected_ = pvalue.as_string_array();
+      for (const auto & exp : expected_) {
         auto item = std::make_shared<StatusItem>(exp);
         this->addItem(exp, item);
       }
diff --git a/diagnostic_aggregator/test/expected_only_analyzer.yaml b/diagnostic_aggregator/test/expected_only_analyzer.yaml
new file mode 100644
index 00000000..c0945652
--- /dev/null
+++ b/diagnostic_aggregator/test/expected_only_analyzer.yaml
@@ -0,0 +1,11 @@
+/**:
+  ros__parameters:
+    log_level: debug
+    # Regression test for the `expected` matcher: an analyzer whose ONLY matcher
+    # is `expected` must still initialise. Prior to the fix this failed because
+    # the `expected` parameter populated the base-class items_ map but never the
+    # expected_ vector that the init guard checks, so the analyzer was dropped.
+    expected_only:
+      type: 'diagnostic_aggregator/GenericAnalyzer'
+      path: ExpectedOnly
+      expected: [ 'some/expected/status' ]
diff --git a/diagnostic_aggregator/test/expected_output/create_expected_only_analyzer.txt b/diagnostic_aggregator/test/expected_output/create_expected_only_analyzer.txt
new file mode 100644
index 00000000..9e56ce19
--- /dev/null
+++ b/diagnostic_aggregator/test/expected_output/create_expected_only_analyzer.txt
@@ -0,0 +1,2 @@
+diagnostic_aggregator/GenericAnalyzer 'ExpectedOnly'
+/ExpectedOnly