diff --git a/skimage/transform/_geometric.py b/skimage/transform/_geometric.py
index 3c14f709..53074c00 100644
--- a/skimage/transform/_geometric.py
+++ b/skimage/transform/_geometric.py
@@ -1074,7 +1074,12 @@ def warp(image, inverse_map=None, map_args={}, output_shape=None, order=1,
     image = np.atleast_3d(img_as_float(image))
     ishape = np.array(image.shape)
     bands = ishape[2]
-    output_shape = np.array(output_shape, dtype=int)
+
+    if output_shape is None:
+        output_shape = ishape
+    else:
+        output_shape = np.array(output_shape, dtype=int)
+
 
     out = None
 
@@ -1111,10 +1116,6 @@ def warp(image, inverse_map=None, map_args={}, output_shape=None, order=1,
                 out = out[..., 0]
 
     if out is None:  # use ndimage.map_coordinates
-
-        if output_shape is None:
-            output_shape = ishape
-
         rows, cols = output_shape[:2]
 
         # inverse_map is a transformation matrix as numpy array
diff --git a/skimage/transform/tests/test_warps.py b/skimage/transform/tests/test_warps.py
index e49ab098..f85125d0 100644
--- a/skimage/transform/tests/test_warps.py
+++ b/skimage/transform/tests/test_warps.py
@@ -248,5 +248,10 @@ def test_inverse():
     assert_array_equal(warp(image, inverse_tform), warp(image, tform.inverse))
 
 
+def test_slow_warp_nonint_oshape():
+    image = np.random.random((5, 5))
+    warp(image, lambda xy: xy, output_shape=(13.1, 19.5))
+
+
 if __name__ == "__main__":
     run_module_suite()