diff --git a/tools/diff_cp2k.py b/tools/diff_cp2k.py
index 0e8ae3ed7a..e7f6428e75 100755
--- a/tools/diff_cp2k.py
+++ b/tools/diff_cp2k.py
@@ -216,14 +216,15 @@ def main():
 
     print("")
 
-    ref=float(files[args.file_lists[args.base-1]][1])
-    color='\033[0m'
-    endc='\033[0m'
-    for filename in args.file_lists:
-        comp=(float(files[filename][1])-ref)/ref
-        if abs(comp)>1e-14: color='\033[91m'
-        else: color='\033[0m'
-        print(('{0} ==> {1} : {2} : '+color+'{3}'+endc).format(files[filename][0],filename,files[filename][1],(float(files[filename][1])-ref)/ref))
+    if len(files[args.file_lists[args.base-1]][1])>0:
+        ref=float(files[args.file_lists[args.base-1]][1])
+        color='\033[0m'
+        endc='\033[0m'
+        for filename in args.file_lists:
+            comp=(float(files[filename][1])-ref)/ref
+            if abs(comp)>1e-14: color='\033[91m'
+            else: color='\033[0m'
+            print(('{0} ==> {1} : {2} : '+color+'{3}'+endc).format(files[filename][0],filename,files[filename][1],(float(files[filename][1])-ref)/ref))
 
     print("")