diff --git a/src/condensed.py b/src/condensed.py
--- a/src/condensed.py
+++ b/src/condensed.py
@@ -52,6 +52,9 @@ import base64
 import binascii
 
 
+class SException(Exception): pass
+
+
 def reconstructRaw(*shares):
 	"""Tries to recover the secret from its shares.
 
@@ -72,8 +75,10 @@ def reconstruct(*shares):
 	:return: (str) reconstructed secret. Too few shares returns garbage."""
 
 	bs=reconstructRaw(*(decode(s) for s in shares))
-	return bs.decode(encoding="utf-8")
-
+	try:
+		return bs.decode(encoding="utf-8")
+	except UnicodeDecodeError:
+		raise SException('Failed to decode bytes to utf-8. Either you supplied invalid shares, or you missed the "raw" flag. Offending value: "{0}"'.format(bs))
 
 
 def decode(share):
@@ -81,12 +86,12 @@ def decode(share):
 		(i,_,shareStr)=share.partition(".")
 		i=int(i)
 		if not 1<=i<=255:
-			raise ValueError()
+			raise SException("Malformed share: Failed 1<=k<=255, k={0}".format(i))
 
 		shareBytes=base64.b32decode(shareStr)
 		return (i,shareBytes)
 	except (ValueError,binascii.Error):
-		raise ValueError('bad share format: share="{0}"'.format(share))
+		raise SException('Malformed share: share="{0}"'.format(share))
 
 ###
 
@@ -109,7 +114,7 @@ def run():
 
 def _reconstruct(args):
 	try: print(reconstruct(*args.share))
-	except ValueError as e: print("operation failed: ",e)
+	except SException as e: print(e)
 
 
 if __name__=="__main__":