diff --git a/sources/diagramcontext.cpp b/sources/diagramcontext.cpp
index 80f4b1569..099f7a6b1 100644
--- a/sources/diagramcontext.cpp
+++ b/sources/diagramcontext.cpp
@@ -18,7 +18,7 @@
 #include "diagramcontext.h"
 #include <QRegExp>
 #include "qet.h"
-#include <algorithm>
+#include <QDebug>
 
 /**
  * @brief DiagramContext::add
@@ -213,7 +213,7 @@ void DiagramContext::fromSettings(QSettings &settings, const QString &array_name
 	@see keyIsAcceptable()
 */
 QString DiagramContext::validKeyRegExp() {
-	return("^[a-z0-9-]+$");
+	return("^[a-z0-9-_]+$");
 }
 
 /**
@@ -231,3 +231,14 @@ bool DiagramContext::keyIsAcceptable(const QString &key) const {
 	QRegExp re(DiagramContext::validKeyRegExp());
 	return(re.exactMatch(key));
 }
+
+QDebug operator <<(QDebug debug, const DiagramContext &context)
+{
+	debug << "DiagramContext";
+	for (auto key : context.keys()) {
+		debug.nospace() << key << " : " << context.value(key) << "\n";
+	}
+	debug << " end DiagramContext";
+
+	return debug;
+}
diff --git a/sources/diagramcontext.h b/sources/diagramcontext.h
index 247bc4159..013353c74 100644
--- a/sources/diagramcontext.h
+++ b/sources/diagramcontext.h
@@ -90,4 +90,6 @@ class DiagramContext
 		QHash<QString, QVariant> m_content;
 		QHash<QString, bool> m_content_show;
 };
+
+QDebug operator <<(QDebug debug, const DiagramContext &context);
 #endif