diff --git a/libfprint/drivers/aes2550.c b/libfprint/drivers/aes2550.c
index 950f5d14..6c432e78 100644
--- a/libfprint/drivers/aes2550.c
+++ b/libfprint/drivers/aes2550.c
@@ -57,6 +57,7 @@ struct _FpiDeviceAes2550
 
   GSList       *strips;
   size_t        strips_len;
+  gboolean      active;
   gboolean      deactivating;
   int           heartbeat_cnt;
 };
@@ -91,14 +92,21 @@ finger_det_data_cb (FpiUsbTransfer *transfer, FpDevice *device,
                     gpointer user_data, GError *error)
 {
   FpImageDevice *dev = FP_IMAGE_DEVICE (device);
+  FpiDeviceAes2550 *self = FPI_DEVICE_AES2550 (device);
   unsigned char *data = transfer->buffer;
 
   if (error)
     {
-      /* Ensure deactivation completes even though the finger-detect
-       * loop is broken by the session error. */
-      fpi_image_device_session_error (dev, error);
-      complete_deactivation (dev);
+      /* The finger-detect loop is broken; it no longer has a pending
+       * operation. Clear the active flag so that the deactivation
+       * triggered by the session error (or an in-flight cancellation)
+       * can complete. */
+      self->active = FALSE;
+
+      if (self->deactivating)
+        complete_deactivation (dev);
+      else
+        fpi_image_device_session_error (dev, error);
       return;
     }
 
@@ -125,13 +133,20 @@ finger_det_reqs_cb (FpiUsbTransfer *t, FpDevice *device,
 {
   FpiUsbTransfer *transfer;
   FpImageDevice *dev = FP_IMAGE_DEVICE (device);
+  FpiDeviceAes2550 *self = FPI_DEVICE_AES2550 (device);
 
   if (error)
     {
-      /* Ensure deactivation completes even though the finger-detect
-       * loop is broken by the session error. */
-      fpi_image_device_session_error (dev, error);
-      complete_deactivation (dev);
+      /* The finger-detect loop is broken; it no longer has a pending
+       * operation. Clear the active flag so that the deactivation
+       * triggered by the session error (or an in-flight cancellation)
+       * can complete. */
+      self->active = FALSE;
+
+      if (self->deactivating)
+        complete_deactivation (dev);
+      else
+        fpi_image_device_session_error (dev, error);
       return;
     }
 
@@ -383,12 +398,12 @@ capture_sm_complete (FpiSsm *ssm, FpDevice *_dev, GError *error)
     }
   else if (error)
     {
-      /* fpi_image_device_session_error() will trigger dev_deactivate()
-       * which sets the deactivating flag. Since the SSM is terminating,
-       * complete_deactivation() must be called here to avoid a deadlock
-       * where nothing checks the deactivating flag. */
+      /* The capture SSM has terminated, so no completion handler is left
+       * to observe the deactivation that the session error triggers.
+       * Clear the active flag so dev_deactivate() completes it directly.
+       */
+      self->active = FALSE;
       fpi_image_device_session_error (dev, error);
-      complete_deactivation (dev);
     }
   else
     {
@@ -506,12 +521,16 @@ activate_run_state (FpiSsm *ssm, FpDevice *dev)
 static void
 activate_sm_complete (FpiSsm *ssm, FpDevice *_dev, GError *error)
 {
+  FpiDeviceAes2550 *self = FPI_DEVICE_AES2550 (_dev);
   FpImageDevice *dev = FP_IMAGE_DEVICE (_dev);
 
   fpi_image_device_activate_complete (dev, error);
 
   if (!error)
-    start_finger_detection (dev);
+    {
+      self->active = TRUE;
+      start_finger_detection (dev);
+    }
 }
 
 static void
@@ -528,6 +547,13 @@ dev_deactivate (FpImageDevice *dev)
 {
   FpiDeviceAes2550 *self = FPI_DEVICE_AES2550 (dev);
 
+  if (!self->active)
+    {
+      /* No operation is pending, so complete it right away. */
+      complete_deactivation (dev);
+      return;
+    }
+
   self->deactivating = TRUE;
 }
 
@@ -539,6 +565,7 @@ complete_deactivation (FpImageDevice *dev)
   G_DEBUG_HERE ();
 
   self->deactivating = FALSE;
+  self->active = FALSE;
   g_slist_free (self->strips);
   self->strips = NULL;
   self->strips_len = 0;