diff --git a/UD_any/print_results.py b/UD_any/print_results.py
index 82393accaecea3947622542bcfef4120142b1bb1..5102a2fb58dc3ef15cf0d2ec3aa2956cad76b85d 100755
--- a/UD_any/print_results.py
+++ b/UD_any/print_results.py
@@ -58,6 +58,11 @@ if __name__ == "__main__" :
         output.append(outputByModelScore[corpus][model][metric][0])
         output[-1][2] = score
 
+  if len(output) == 0 :
+    print("ERROR : Output length is 0", file=sys.stderr)
+    print("  did you run evaluate.sh ?", file=sys.stderr)
+    exit(1)
+
   maxColLens = [0 for _ in range(len(output[0]))]
 
   output = [["Corpus","Metric","F1.score","Model"]] + output