diff --git a/src/mana_plugin_root_histogram.cc b/src/mana_plugin_root_histogram.cc
index 11ab4bc..a87bc27 100644
--- a/src/mana_plugin_root_histogram.cc
+++ b/src/mana_plugin_root_histogram.cc
@@ -20,18 +20,30 @@ struct Context
     std::vector<std::vector<TH1 *>> rawHistograms;
 };
 
+static Context *g_ctx = nullptr;
+
 MANA_DEFINE_PLUGIN_INIT(init)
 {
+    if (g_ctx)
+    {
+        log_warn("init() called multiple times. This plugin is a singleton!");
+        return g_ctx;
+    }
     log_set_level(LOG_INFO);
-    static Context g_ctx;
-    log_debug("init: ctx=%p", &g_ctx);
-    return &g_ctx;
+    log_debug("init");
+    return g_ctx = new Context;
 }
 
 MANA_DEFINE_PLUGIN_SHUTDOWN(shutdown)
 {
-    (void)context;
     log_debug("shutdown");
+    if (context != g_ctx)
+    {
+        log_warn("shutdown() called with invalid context");
+        return;
+    }
+    delete g_ctx;
+    g_ctx = nullptr;
 }
 
 struct ObjectPath
@@ -145,7 +157,8 @@ inline std::string histo_info(const std::vector<std::vector<TH1 *>> &histos)
         }
     }
 
-    return fmt::format("histoCount={}, histoMem={} MiB", histoCount, histoMem / (1024.0 * 1024));
+    return fmt::format("histoCount={}, histoMem={:.2f} MiB", histoCount,
+                       histoMem / (1024.0 * 1024));
 }
 
 MANA_DEFINE_PLUGIN_BEGIN_RUN(begin_run)