diff --git a/src/control/settings/MetadataManager.cpp b/src/control/settings/MetadataManager.cpp
index dd1113f7..fb6374b1 100644
--- a/src/control/settings/MetadataManager.cpp
+++ b/src/control/settings/MetadataManager.cpp
@@ -140,7 +140,7 @@ MetadataEntry MetadataManager::loadMetadataFile(string path, string file)
 	ifstream infile(path.c_str());
 
 	string time = file.substr(0, file.size() - 9);
-	entry.time = std::stol(time);
+	entry.time = strtoll(time.c_str(), NULL, 10);
 
 	if (!getline(infile, line))
 	{
@@ -165,7 +165,6 @@ MetadataEntry MetadataManager::loadMetadataFile(string path, string file)
 
 	entry.path = line;
 
-
 	if (!getline(infile, line))
 	{
 		deleteMetadataFile(path);
@@ -180,15 +179,7 @@ MetadataEntry MetadataManager::loadMetadataFile(string path, string file)
 		return entry;
 	}
 
-	try
-	{
-		entry.page = std::stoi(line.substr(5));
-	}
-	catch (const std::exception& e)
-	{
-		// Return invalid entry
-		return entry;
-	}
+	entry.page = strtoll(line.substr(5).c_str(), NULL, 10);
 
 	if (!getline(infile, line))
 	{
@@ -204,7 +195,7 @@ MetadataEntry MetadataManager::loadMetadataFile(string path, string file)
 		return entry;
 	}
 
-	entry.zoom = std::stod(line.substr(5));
+	entry.zoom = strtod(line.substr(5).c_str(), NULL);
 
 	entry.valid = true;
 	return entry;
diff --git a/src/control/xojfile/LoadHandler.cpp b/src/control/xojfile/LoadHandler.cpp
index 84334e19..20d1454e 100644
--- a/src/control/xojfile/LoadHandler.cpp
+++ b/src/control/xojfile/LoadHandler.cpp
@@ -5,6 +5,7 @@
 #include "LoadHandlerHelper.h"
 
 #include <config.h>
+#include <GzUtil.h>
 #include <i18n.h>
 
 #include <glib/gstdio.h>
@@ -116,7 +117,7 @@ bool LoadHandler::openFile(string filename)
 	XOJ_CHECK_TYPE(LoadHandler);
 
 	this->filename = filename;
-	this->fp = gzopen(filename.c_str(), "r");
+	this->fp = GzUtil::openPath(filename, "r");
 	if (!this->fp)
 	{
 		this->lastError = FS(_F("Could not open file: \"{1}\"") % filename);
diff --git a/src/gui/toolbarMenubar/model/ToolbarColorNames.cpp b/src/gui/toolbarMenubar/model/ToolbarColorNames.cpp
index 8d473d7b..ebdbc73e 100644
--- a/src/gui/toolbarMenubar/model/ToolbarColorNames.cpp
+++ b/src/gui/toolbarMenubar/model/ToolbarColorNames.cpp
@@ -4,11 +4,7 @@
 #include <i18n.h>
 #include <StringUtils.h>
 
-#include <stdio.h>
-#include <fstream>
-#include <iostream>
-using std::cout;
-using std::endl;
+#include <glib/gstdio.h>
 
 ToolbarColorNames::ToolbarColorNames()
 {
@@ -70,9 +66,15 @@ void ToolbarColorNames::saveFile(const string file)
 	gsize len = 0;
 	char* data = g_key_file_to_data(this->config, &len, NULL);
 
-	std::ofstream f(file, std::fstream::out);
-	f << data;
-	f.close();
+	FILE* fp = g_fopen(file.c_str(), "wb");
+	if (!fp)
+	{
+		g_error("Could not save color file «%s»", file.c_str());
+		return;
+	}
+
+	fwrite(data, len, 1, fp);
+	fclose(fp);
 
 	g_free(data);
 }
diff --git a/src/util/GzUtil.cpp b/src/util/GzUtil.cpp
new file mode 100644
index 00000000..4bac46d8
--- /dev/null
+++ b/src/util/GzUtil.cpp
@@ -0,0 +1,14 @@
+#include "GzUtil.h"
+
+gzFile GzUtil::openPath(Path path, string flags)
+{
+#ifdef WIN32
+	wchar_t* wfilename = (wchar_t*)g_utf8_to_utf16(path.c_str(), -1, NULL, NULL, NULL);
+	gzFile fp = gzopen_w(wfilename, flags.c_str());
+	g_free(wfilename);
+
+	return fp;
+#else
+	return gzopen(path.c_str(), flags.c_str());
+#endif
+}
diff --git a/src/util/GzUtil.h b/src/util/GzUtil.h
new file mode 100644
index 00000000..0c0e4133
--- /dev/null
+++ b/src/util/GzUtil.h
@@ -0,0 +1,26 @@
+/*
+ * Xournal++
+ *
+ * Gzip Helper
+ *
+ * @author Xournal++ Team
+ * https://github.com/xournalpp/xournalpp
+ *
+ * @license GNU GPLv2 or later
+ */
+
+#pragma once
+
+#include "Path.h"
+#include <zlib.h>
+
+class GzUtil
+{
+private:
+	GzUtil();
+	virtual ~GzUtil();
+
+public:
+	static gzFile openPath(Path path, string flags);
+};
+
diff --git a/src/util/OutputStream.cpp b/src/util/OutputStream.cpp
index 3d3ab5fa..234c5280 100644
--- a/src/util/OutputStream.cpp
+++ b/src/util/OutputStream.cpp
@@ -1,5 +1,6 @@
 #include "OutputStream.h"
 
+#include "GzUtil.h"
 #include <i18n.h>
 
 #include <stdlib.h>
@@ -29,7 +30,7 @@ GzOutputStream::GzOutputStream(Path filename)
 	this->fp = NULL;
 	this->filename = filename;
 
-	this->fp = gzopen(filename.c_str(), "w");
+	this->fp = GzUtil::openPath(filename, "w");
 	if (this->fp == NULL)
 	{
 		this->error = FS(_F("Error opening file: \"{1}\"") % filename.str());
diff --git a/src/util/XojPreviewExtractor.cpp b/src/util/XojPreviewExtractor.cpp
index 99d89b20..6f4d90e9 100644
--- a/src/util/XojPreviewExtractor.cpp
+++ b/src/util/XojPreviewExtractor.cpp
@@ -4,6 +4,8 @@
 #include <zlib.h>
 #include <string.h>
 
+#include <GzUtil.h>
+
 const char* TAG_PREVIEW_NAME = "preview";
 const int TAG_PREVIEW_NAME_LEN = strlen(TAG_PREVIEW_NAME);
 const char* TAG_PAGE_NAME = "page";
@@ -109,7 +111,7 @@ PreviewExtractResult XojPreviewExtractor::readFile(Path file)
 		return PREVIEW_RESULT_BAD_FILE_EXTENSION;
 	}
 
-	gzFile fp = gzopen(file.c_str(), "r");
+	gzFile fp = GzUtil::openPath(file, "r");
 	if (!fp)
 	{
 		return PREVIEW_RESULT_COULD_NOT_OPEN_FILE;
diff --git a/src/xoj-preview-extractor/CMakeLists.txt b/src/xoj-preview-extractor/CMakeLists.txt
index 731a5b95..527727b6 100644
--- a/src/xoj-preview-extractor/CMakeLists.txt
+++ b/src/xoj-preview-extractor/CMakeLists.txt
@@ -7,6 +7,7 @@ endif ()
 
 add_executable (xournal-thumbnailer
   xournal-thumbnailer.cpp
+  "${PROJECT_SOURCE_DIR}/src/util/GzUtil.cpp"
   "${PROJECT_SOURCE_DIR}/src/util/Path.cpp"
   "${PROJECT_SOURCE_DIR}/src/util/PlaceholderString.cpp"
   "${PROJECT_SOURCE_DIR}/src/util/StringUtils.cpp"