diff --git a/src/util/report_manager.cpp b/src/util/report_manager.cpp
index 9c72da07..6f6bd0e8 100644
--- a/src/util/report_manager.cpp
+++ b/src/util/report_manager.cpp
@@ -174,8 +174,9 @@ u32 ReportManager::getDkey(const Report &r) const {
 
 void ReportManager::registerExtReport(ReportID id,
                                       const external_report_info &ext) {
-    if (contains(externalIdMap, id)) {
-        const external_report_info &eri = externalIdMap.at(id);
+    auto it = externalIdMap.find(id);
+    if (it != externalIdMap.end()) {
+        const external_report_info &eri = it->second;
         if (eri.highlander != ext.highlander) {
             /* we have a problem */
             ostringstream out;
diff --git a/src/util/report_manager.h b/src/util/report_manager.h
index f76aff22..3fcad330 100644
--- a/src/util/report_manager.h
+++ b/src/util/report_manager.h
@@ -38,6 +38,7 @@
 #include "util/compile_error.h"
 #include "util/noncopyable.h"
 #include "util/report.h"
+#include "util/ue2_containers.h"
 
 #include <map>
 #include <set>
@@ -140,7 +141,7 @@ private:
 
     /** \brief Mapping from external match ids to information about that
      * id. */
-    std::map<ReportID, external_report_info> externalIdMap;
+    unordered_map<ReportID, external_report_info> externalIdMap;
 
     /** \brief Mapping from expression index to exhaustion key. */
     std::map<s64a, u32> toExhaustibleKeyMap;