diff --git a/src/process.py b/src/process.py
index 40f8f768cfdecb89bd01987ac8c503c2b204b9f2..c82cac12e700d41c2443d7f67b28a1f89d0448fa 100644
--- a/src/process.py
+++ b/src/process.py
@@ -462,6 +462,8 @@ class Process(Nextflow_Building_Blocks):
         #code = process_2_DSL2(code) 
         lines = []
         for line in code.split("\n"):
+            if(" def " in " "+line):
+                raise BioFlowInsightError(f"[DSL1 converter error] Do not recognise the input '{line.strip()}' in the process '{self.get_name()}'. Try rewritting it in a different way.")
             temp = process_2_DSL2(line.split(" from ")[0]) 
             lines.append(temp)
             #TODO -> need to determine if it's on it's own is it either a path or val