diff --git a/backend/genesys_devices.c b/backend/genesys_devices.c
index f21bcc6d5..c05790f8e 100644
--- a/backend/genesys_devices.c
+++ b/backend/genesys_devices.c
@@ -1079,6 +1079,7 @@ static Genesys_Model hp3670c_model = {
   MOTOR_HP3670,
       GENESYS_FLAG_LAZY_INIT
     | GENESYS_FLAG_14BIT_GAMMA
+    | GENESYS_FLAG_XPA
     | GENESYS_FLAG_DARK_CALIBRATION
     | GENESYS_FLAG_OFFSET_CALIBRATION
     | GENESYS_FLAG_SKIP_WARMUP
diff --git a/backend/genesys_gl646.c b/backend/genesys_gl646.c
index 87d7162eb..2f60e3c5a 100644
--- a/backend/genesys_gl646.c
+++ b/backend/genesys_gl646.c
@@ -859,6 +859,13 @@ gl646_setup_registers (Genesys_Device * dev,
   /* regs[reg_0x03].value |= REG03_AVEENB; */
   regs[reg_0x03].value &= ~REG03_LAMPDOG;
 
+  /* select XPA */
+  regs[reg_0x03].value &= ~REG03_XPASEL;
+  if(scan_settings.scan_method == SCAN_METHOD_TRANSPARENCY)
+    {
+      regs[reg_0x03].value |= REG03_XPASEL;
+    }
+
   /* R04 */
   if (depth > 8)
     {
@@ -4959,6 +4966,29 @@ gl646_update_hardware_sensors (Genesys_Scanner * session)
 	  return SANE_STATUS_UNSUPPORTED;
 	}
     }
+
+  /* XPA detection */
+  if (dev->model->flags & GENESYS_FLAG_XPA)
+    {
+      switch (dev->model->gpo_type)
+	{
+	case GPO_HP3670:
+          /* test if XPA is plugged-in */
+          if((value & 0x40)==0)
+            {
+              DBG (DBG_io, "gl646_update_hardware_sensors: enabling XPA\n");
+              session->opt[OPT_SOURCE].cap &= ~SANE_CAP_INACTIVE;
+            }
+          else
+            {
+              DBG (DBG_io, "gl646_update_hardware_sensors: disabling XPA\n");
+              session->opt[OPT_SOURCE].cap |= SANE_CAP_INACTIVE;
+            }
+	  break;
+	default:
+	  return SANE_STATUS_UNSUPPORTED;
+	}
+    }
   
   return status;
 }
diff --git a/backend/genesys_low.h b/backend/genesys_low.h
index d67597a14..a65613e31 100644
--- a/backend/genesys_low.h
+++ b/backend/genesys_low.h
@@ -77,7 +77,7 @@
 #define GENESYS_FLAG_UNTESTED     (1 << 0)	/* Print a warning for these scanners */
 #define GENESYS_FLAG_14BIT_GAMMA  (1 << 1)	/* use 14bit Gamma table instead of 12 */
 #define GENESYS_FLAG_LAZY_INIT    (1 << 2)	/* skip extensive ASIC test at init   */
-/*#define GENESYS_FLAG_UNUSED     (1 << 3)	*/
+#define GENESYS_FLAG_XPA          (1 << 3)
 #define GENESYS_FLAG_SKIP_WARMUP  (1 << 4)	/* skip genesys_warmup()              */
 #define GENESYS_FLAG_OFFSET_CALIBRATION   (1 << 5)	/* do offset calibration      */
 #define GENESYS_FLAG_SEARCH_START (1 << 6)	/* do start search beofre scanning    */