diff --git a/pyopencl/array.py b/pyopencl/array.py
index fb80f2d70..27607c7b6 100644
--- a/pyopencl/array.py
+++ b/pyopencl/array.py
@@ -2604,11 +2604,19 @@ def make_func_for_chunk_size(chunk_size):
 
 def concatenate(arrays, axis=0, queue=None, allocator=None):
     """
+    Return a :class:`Array` that is a concatenation of the input tuple of
+    :class:`Array` along :arg axis:. **Warning** The current implementation
+    allows only concatenation of row-major arrays along axis = 0.
+
     .. versionadded:: 2013.1
     """
     # {{{ find properties of result array
 
     shape = None
+    if axis != 0:
+        raise NotImplementedError("Axis != 0. "
+                                  + "To be implemented when Array.setitems "
+                                  + "allows values with different stride.")
 
     for i_ary, ary in enumerate(arrays):
         queue = queue or ary.queue