diff --git a/CMakeLists.txt b/CMakeLists.txt
index a2a0c94..dce806c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,16 +15,35 @@ option(BUILD_GUI "Build the GTK UI" ON)
 option(BUILD_CLI "Build the CLI" ON)
 
 set(CMAKE_C_STANDARD 11)
-set(CMAKE_C_FLAGS "-Wall -Wextra -O2 -Wformat=2 -Wmissing-format-attribute -fstack-protector-strong -Wundef -Wmissing-format-attribute")
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fdiagnostics-color=always -Wstrict-prototypes -Wunreachable-code")
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wchar-subscripts -Wwrite-strings -Wpointer-arith -Wbad-function-cast -Wcast-align")
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Werror=format-security -Werror=implicit-function-declaration -Wno-sign-compare")
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2")
+set(COMMON_C_FLAGS
+        "-Wall -Wextra -O3 -Wformat=2 -Wmissing-format-attribute -fstack-protector-strong"
+        "-Wundef -Wmissing-format-attribute -fdiagnostics-color=always"
+        "-Wstrict-prototypes -Wunreachable-code -Wchar-subscripts"
+        "-Wwrite-strings -Wpointer-arith -Wbad-function-cast -Wcast-align"
+        "-Werror=format-security -Werror=implicit-function-declaration -Wno-sign-compare"
+        "-U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=3"
+)
+
 if(CMAKE_COMPILER_IS_GNUCC)
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -pie -fPIE")
+    list(APPEND COMMON_C_FLAGS "-pie -fPIE")
 endif()
+
 if(IS_FLATPAK)
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DIS_FLATPAK")
+    list(APPEND COMMON_C_FLAGS "-DIS_FLATPAK")
+endif()
+
+string(REPLACE ";" " " COMMON_C_FLAGS "${COMMON_C_FLAGS}")
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${COMMON_C_FLAGS}")
+
+if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+    set(COMMON_LINKER_FLAGS
+            "-Wl,--no-add-needed -Wl,--as-needed -Wl,--no-undefined"
+            "-Wl,-z,relro,-z,now"
+    )
+
+    string(REPLACE ";" " " COMMON_LINKER_FLAGS "${COMMON_LINKER_FLAGS}")
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${COMMON_LINKER_FLAGS}")
+    set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} ${COMMON_LINKER_FLAGS}")
 endif()
 
 add_definitions(-DGETTEXT_PACKAGE=\"${GETTEXT_PACKAGE}\")
@@ -83,22 +102,22 @@ if(BUILD_GUI)
     set_target_properties(${PROJECT_NAME} PROPERTIES OUTPUT_NAME "otpclient")
 
     install(TARGETS ${PROJECT_NAME} DESTINATION bin)
-
     install(FILES data/com.github.paolostivanin.OTPClient.desktop DESTINATION share/applications)
+    install(FILES man/otpclient.1.gz DESTINATION share/man/man1)
 
-    install(FILES
+    set(GUI_UI_FILES
             src/gui/ui/otpclient.ui
             src/gui/ui/add_popover.ui
             src/gui/ui/settings_popover.ui
             src/gui/ui/shortcuts.ui
-            DESTINATION share/otpclient)
-
-    install(FILES man/otpclient.1.gz DESTINATION share/man/man1)
+    )
+    install(FILES ${GUI_UI_FILES} DESTINATION share/otpclient)
 
-    install(FILES
+    set(GUI_ICON_FILES
             data/icons/com.github.paolostivanin.OTPClient.svg
             data/icons/com.github.paolostivanin.OTPClient-symbolic.svg
-            DESTINATION share/icons/hicolor/scalable/apps)
+    )
+    install(FILES ${GUI_ICON_FILES} DESTINATION share/icons/hicolor/scalable/apps)
 endif ()
 
 if(BUILD_CLI)
@@ -109,7 +128,6 @@ if(BUILD_CLI)
     set_target_properties(${PROJECT_NAME}-cli PROPERTIES OUTPUT_NAME "otpclient-cli")
 
     install(TARGETS ${PROJECT_NAME}-cli DESTINATION bin)
-
     install(FILES man/otpclient-cli.1.gz DESTINATION share/man/man1)
 endif()
 
diff --git a/src/gui/gui-misc.c b/src/gui/gui-misc.c
index 0bacbbc..1e1499d 100644
--- a/src/gui/gui-misc.c
+++ b/src/gui/gui-misc.c
@@ -193,7 +193,7 @@ decode_migration_data (const gchar *encoded_uri)
         return NULL;
     }
     encoded_uri_copy += 33;
-    gsize out_len;
+    gsize out_len = 0;
     gchar *unesc_str = g_uri_unescape_string_secure (encoded_uri_copy, NULL);
     guchar *data = g_base64_decode_secure (unesc_str, &out_len);
     gcry_free (unesc_str);
diff --git a/src/gui/ui/otpclient.ui b/src/gui/ui/otpclient.ui
index e645875..8b78b37 100644
--- a/src/gui/ui/otpclient.ui
+++ b/src/gui/ui/otpclient.ui
@@ -265,6 +265,8 @@
     <property name="window-position">center</property>
     <property name="type-hint">dialog</property>
     <property name="gravity">center</property>
+    <property name="default-width">400</property>
+    <property name="default-height">200</property>
     <child internal-child="vbox">
       <object class="GtkBox">
         <property name="can-focus">False</property>