diff --git a/lib/damask/__init__.py b/lib/damask/__init__.py
index eedfdd0c0..1875ffdae 100644
--- a/lib/damask/__init__.py
+++ b/lib/damask/__init__.py
@@ -1,7 +1,13 @@
 # -*- coding: UTF-8 no BOM -*-
 
 """Main aggregator"""
-import os,sys
+import os,sys,time
+
+h5py_flag = os.path.join(os.path.dirname(__file__),'../../.noH5py')
+h5py_grace = 7200                         # only complain once every 7200 sec (2 hours)
+h5py_msg = "h5py module not found."
+
+now = time.time()
 
 with open(os.path.join(os.path.dirname(__file__),'../../VERSION')) as f:
   version = f.readline()[:-1]
@@ -9,9 +15,18 @@ with open(os.path.join(os.path.dirname(__file__),'../../VERSION')) as f:
 from .environment import Environment      # noqa
 from .asciitable  import ASCIItable       # noqa
 try:
-  from .h5table     import H5Table        # noqa
+  from .h5table   import H5Table          # noqa
+  if os.path.exists(h5py_flag): os.remove(h5py_flag)  # delete flagging file on success
 except ImportError:
-  sys.stderr.write("h5py module not found")
+  if os.path.exists(h5py_flag):
+    if now - os.path.getmtime(h5py_flag) > h5py_grace: # complain (again) every so-and-so often
+      sys.stderr.write(h5py_msg+'\n')
+      with open(h5py_flag, 'a'):
+        os.utime(h5py_flag,(now,now))     # update flag modification time to "now"
+  else:
+    open(h5py_flag, 'a').close()          # create flagging file
+    sys.stderr.write(h5py_msg+'\n')       # complain for the first time
+    
 from .config      import Material         # noqa
 from .colormaps   import Colormap, Color  # noqa
 from .orientation import Quaternion, Rodrigues, Symmetry, Orientation # noqa