diff --git a/reader/JFJochHDF5Reader.cpp b/reader/JFJochHDF5Reader.cpp
index afc162ca..9acbc39a 100644
--- a/reader/JFJochHDF5Reader.cpp
+++ b/reader/JFJochHDF5Reader.cpp
@@ -98,7 +98,7 @@ std::string dataset_name(const std::string& path) {
 }
 
 void JFJochHDF5Reader::ReadFile(const std::string& filename) {
-    std::unique_lock ul(file_mutex);
+    std::unique_lock ul(hdf5_mutex);
     try {
         auto dataset = std::make_shared<JFJochReaderDataset>();
         master_file = std::make_unique<HDF5ReadOnlyFile>(filename);
@@ -448,7 +448,7 @@ void JFJochHDF5Reader::ReadFile(const std::string& filename) {
 }
 
 uint64_t JFJochHDF5Reader::GetNumberOfImages() const {
-    std::unique_lock ul(file_mutex);
+    std::unique_lock ul(hdf5_mutex);
     return number_of_images;
 }
 
@@ -490,7 +490,7 @@ bool JFJochHDF5Reader::LoadImage_i(std::shared_ptr<JFJochReaderDataset> &dataset
                                    std::vector<uint8_t> &buffer,
                                    int64_t image_number,
                                    bool update_dataset) {
-    std::unique_lock ul(file_mutex);
+    std::unique_lock ul(hdf5_mutex);
 
     if (!dataset)
         return {};
@@ -709,7 +709,7 @@ bool JFJochHDF5Reader::LoadImage_i(std::shared_ptr<JFJochReaderDataset> &dataset
 }
 
 void JFJochHDF5Reader::Close() {
-    std::unique_lock ul(file_mutex);
+    std::unique_lock ul(hdf5_mutex);
     master_file = {};
     number_of_images = 0;
     legacy_format_files.clear();
diff --git a/reader/JFJochHDF5Reader.h b/reader/JFJochHDF5Reader.h
index b7603869..914050ab 100644
--- a/reader/JFJochHDF5Reader.h
+++ b/reader/JFJochHDF5Reader.h
@@ -8,7 +8,6 @@
 #include "../writer/HDF5Objects.h"
 
 class JFJochHDF5Reader : public JFJochReader {
-    mutable std::mutex file_mutex;
     std::unique_ptr<HDF5ReadOnlyFile> master_file;
 
     std::vector<std::string> legacy_format_files;
diff --git a/writer/HDF5Objects.cpp b/writer/HDF5Objects.cpp
index 81442a88..df243072 100644
--- a/writer/HDF5Objects.cpp
+++ b/writer/HDF5Objects.cpp
@@ -869,7 +869,10 @@ std::string HDF5Object::GetString(const std::string &name, const std::string &de
 }
 
 bool HDF5Object::Exists(const std::string &name) const {
-    return H5Lexists(GetID(), name.c_str(), H5P_DEFAULT) > 0;
+    H5E_BEGIN_TRY {
+        return H5Lexists(GetID(), name.c_str(), H5P_DEFAULT) > 0;
+    } H5E_END_TRY;
+    return false;
 }
 
 herr_t func(hid_t group, const char *name, const H5L_info2_t *info, void *op_data) {