diff --git a/src/toolbox_scs/mnemonics_machinery.py b/src/toolbox_scs/mnemonics_machinery.py
index d61ca5402d75a84baef331e826d576546f5e1e6c..10a42d9f4ba896f00eec407071d772956febf591 100644
--- a/src/toolbox_scs/mnemonics_machinery.py
+++ b/src/toolbox_scs/mnemonics_machinery.py
@@ -10,7 +10,6 @@ import logging
 
 from .constants import mnemonics as _mnemonics
 from extra_data import open_run
-from numpy import s_
 __all__ = [
     'mnemonics_for_run'
 ]
@@ -74,7 +73,9 @@ def mnemo_version_index(run, mnemonic):
 
     """
     if len(_mnemonics[mnemonic]) == 1:
-        return 0
+        if _mnemonics[mnemonic][0]['source'] in run.all_sources:
+            return 0
+        return -1
     for i, v in enumerate(_mnemonics[mnemonic]):
         if (v['source'] in run.all_sources and
                 v['key'] in run.keys_for_source(v['source'])):