diff --git a/src/cairo-surface.c b/src/cairo-surface.c
index ea51d2f86..24db00a7c 100644
--- a/src/cairo-surface.c
+++ b/src/cairo-surface.c
@@ -812,7 +812,9 @@ _cairo_surface_set_device_scale (cairo_surface_t *surface,
     surface->device_transform.yx = 0.0;
 
     surface->device_transform_inverse = surface->device_transform;
-    cairo_matrix_invert (&surface->device_transform_inverse);
+    status = cairo_matrix_invert (&surface->device_transform_inverse);
+    /* should always be invertible unless given pathological input */
+    assert (status == CAIRO_STATUS_SUCCESS);
 }
 
 /**
@@ -854,7 +856,9 @@ cairo_surface_set_device_offset (cairo_surface_t *surface,
     surface->device_transform.y0 = y_offset;
 
     surface->device_transform_inverse = surface->device_transform;
-    cairo_matrix_invert (&surface->device_transform_inverse);
+    status = cairo_matrix_invert (&surface->device_transform_inverse);
+    /* should always be invertible unless given pathological input */
+    assert (status == CAIRO_STATUS_SUCCESS);
 }
 slim_hidden_def (cairo_surface_set_device_offset);
 
diff --git a/src/cairo-svg-surface.c b/src/cairo-svg-surface.c
index ecb716373..8095aa48f 100644
--- a/src/cairo-svg-surface.c
+++ b/src/cairo-svg-surface.c
@@ -1033,7 +1033,6 @@ _cairo_svg_surface_emit_composite_image_pattern (cairo_output_stream_t   *output
 						 const cairo_matrix_t	 *parent_matrix,
 						 const char		 *extra_attributes)
 {
-    cairo_surface_attributes_t surface_attr;
     cairo_rectangle_int_t extents;
     cairo_status_t status;
     cairo_matrix_t p2u;