diff --git a/debian/libnfc4.symbols b/debian/libnfc4.symbols
index 48a856d..2437b36 100644
--- a/debian/libnfc4.symbols
+++ b/debian/libnfc4.symbols
@@ -54,5 +54,4 @@ libnfc.so.4 libnfc4 #MINVER#
  str_nfc_baud_rate@Base 1.7.0~rc2
  str_nfc_modulation_type@Base 1.7.0~rc2
  str_nfc_target@Base 1.7.0~rc2
- usb_initialized@Base 1.7.0~rc6-0
  usb_prepare@Base 1.7.0~rc6-0
diff --git a/libnfc/buses/usbbus.c b/libnfc/buses/usbbus.c
index a2294da..6c0abdd 100644
--- a/libnfc/buses/usbbus.c
+++ b/libnfc/buses/usbbus.c
@@ -32,13 +32,12 @@
 #define LOG_CATEGORY "libnfc.buses.usbbus"
 #define LOG_GROUP    NFC_LOG_GROUP_DRIVER
 
-// Global flag to know if usb_init() has already been called or not
-bool usb_initialized = false;
-
 int usb_prepare(void)
 {
-  if (usb_initialized)
+  static bool usb_initialized = false;
+  if (usb_initialized) {
     return 0;
+  }
   usb_init();
   usb_initialized = true;
 
diff --git a/libnfc/buses/usbbus.h b/libnfc/buses/usbbus.h
index 5c08137..329160a 100644
--- a/libnfc/buses/usbbus.h
+++ b/libnfc/buses/usbbus.h
@@ -41,9 +41,6 @@
 #include <stdbool.h>
 #include <string.h>
 
-// Global flag to know if usb_init() has already been called or not
-extern bool usb_initialized;
-
 int usb_prepare(void);
 
 #endif // __NFC_BUS_USB_H__