diff --git a/.gitmodules b/.gitmodules
index d04a3132..66e9825a 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -17,3 +17,9 @@
 	path = third-party/pugixml
 	url = https://github.com/zeux/pugixml
 	branch = master
+[submodule "third-party/botan"]
+	path = third-party/botan
+	url = https://github.com/randombit/botan
+[submodule "third-party/pole"]
+	path = third-party/pole
+	url = https://github.com/catlan/pole
diff --git a/source/worksheet/worksheet.cpp b/source/worksheet/worksheet.cpp
index af732667..0313dc41 100644
--- a/source/worksheet/worksheet.cpp
+++ b/source/worksheet/worksheet.cpp
@@ -275,6 +275,9 @@ void worksheet::set_title(const std::string &title)
 		throw invalid_sheet_title(title);
 	}
 
+	get_workbook().d_->sheet_title_rel_id_map_[title] = 
+		get_workbook().d_->sheet_title_rel_id_map_[d_->title_];
+	get_workbook().d_->sheet_title_rel_id_map_.erase(d_->title_);
 	d_->title_ = title;
 }
 
diff --git a/third-party/botan b/third-party/botan
new file mode 160000
index 00000000..35657e0f
--- /dev/null
+++ b/third-party/botan
@@ -0,0 +1 @@
+Subproject commit 35657e0f76931f0d3a333610e7065c81c35e9f1e
diff --git a/third-party/pole b/third-party/pole
new file mode 160000
index 00000000..0f8eadd8
--- /dev/null
+++ b/third-party/pole
@@ -0,0 +1 @@
+Subproject commit 0f8eadd8b9600cf1254b1efb702d2fe49ae00b71