diff --git a/libfprint/drivers/aes1610.c b/libfprint/drivers/aes1610.c
index 0d3ca4a..e597772 100644
--- a/libfprint/drivers/aes1610.c
+++ b/libfprint/drivers/aes1610.c
@@ -590,8 +590,7 @@ static void capture_read_strip_cb(FpiUsbTransfer *transfer, FpDevice *device,
 		/* send stop capture bits */
 		aes_write_regv(dev, capture_stop, G_N_ELEMENTS(capture_stop), stub_capture_stop_cb, NULL);
 		self->strips = g_slist_reverse(self->strips);
-		fpi_do_movement_estimation(&assembling_ctx, self->strips,
-					   self->strips_len);
+		fpi_do_movement_estimation(&assembling_ctx, self->strips);
 		img = fpi_assemble_frames(&assembling_ctx, self->strips,
 					  self->strips_len);
 
diff --git a/libfprint/drivers/aes2501.c b/libfprint/drivers/aes2501.c
index 50b3498..bb94d65 100644
--- a/libfprint/drivers/aes2501.c
+++ b/libfprint/drivers/aes2501.c
@@ -435,8 +435,7 @@ static void capture_read_strip_cb(FpiUsbTransfer *transfer, FpDevice *_dev,
 			FpImage *img;
 
 			self->strips = g_slist_reverse(self->strips);
-			fpi_do_movement_estimation(&assembling_ctx,
-					self->strips, self->strips_len);
+			fpi_do_movement_estimation(&assembling_ctx, self->strips);
 			img = fpi_assemble_frames(&assembling_ctx,
 						  self->strips,
 						  self->strips_len);
diff --git a/libfprint/drivers/elan.c b/libfprint/drivers/elan.c
index 2c4e3be..3608897 100644
--- a/libfprint/drivers/elan.c
+++ b/libfprint/drivers/elan.c
@@ -302,7 +302,7 @@ static void elan_submit_image(FpImageDevice *dev)
 	assembling_ctx.frame_height = self->frame_height;
 	assembling_ctx.image_width = self->frame_width * 3 / 2;
 	g_slist_foreach(raw_frames, (GFunc) self->process_frame, &frames);
-	fpi_do_movement_estimation(&assembling_ctx, frames, num_frames);
+	fpi_do_movement_estimation(&assembling_ctx, frames);
 	img = fpi_assemble_frames(&assembling_ctx, frames, num_frames);
 
 	fpi_image_device_image_captured(dev, img);
diff --git a/libfprint/fpi-assembling.c b/libfprint/fpi-assembling.c
index ccd9643..116d01d 100644
--- a/libfprint/fpi-assembling.c
+++ b/libfprint/fpi-assembling.c
@@ -173,7 +173,6 @@ do_movement_estimation (struct fpi_frame_asmbl_ctx *ctx,
  * fpi_do_movement_estimation:
  * @ctx: #fpi_frame_asmbl_ctx - frame assembling context
  * @stripes: a singly-linked list of #fpi_frame
- * @num_stripes: number of items in @stripes to process
  *
  * fpi_do_movement_estimation() estimates the movement between adjacent
  * frames, populating @delta_x and @delta_y values for each #fpi_frame.
@@ -181,18 +180,13 @@ do_movement_estimation (struct fpi_frame_asmbl_ctx *ctx,
  * This function is used for devices that don't do movement estimation
  * in hardware. If hardware movement estimation is supported, the driver
  * should populate @delta_x and @delta_y instead.
- *
- * Note that @num_stripes might be shorter than the length of the list,
- * if some stripes should be skipped.
  */
 void
 fpi_do_movement_estimation (struct fpi_frame_asmbl_ctx *ctx,
-                            GSList *stripes, size_t num_stripes)
+                            GSList *stripes)
 {
   int err, rev_err;
 
-  g_return_if_fail (g_slist_length(stripes) != num_stripes);
-
   err = do_movement_estimation (ctx, stripes, FALSE);
   rev_err = do_movement_estimation (ctx, stripes, TRUE);
   fp_dbg ("errors: %d rev: %d", err, rev_err);
diff --git a/libfprint/fpi-assembling.h b/libfprint/fpi-assembling.h
index ae9adc2..33adcfd 100644
--- a/libfprint/fpi-assembling.h
+++ b/libfprint/fpi-assembling.h
@@ -65,8 +65,7 @@ struct fpi_frame_asmbl_ctx
 };
 
 void fpi_do_movement_estimation (struct fpi_frame_asmbl_ctx *ctx,
-                                 GSList                     *stripes,
-                                 size_t                      num_stripes);
+                                 GSList                     *stripes);
 
 FpImage *fpi_assemble_frames (struct fpi_frame_asmbl_ctx *ctx,
                               GSList                     *stripes,