diff --git a/pym/builder/variables/builder.py b/pym/builder/variables/builder.py
index 2a0cb06..daed32c 100644
--- a/pym/builder/variables/builder.py
+++ b/pym/builder/variables/builder.py
@@ -1189,6 +1189,8 @@ class KernelData(ReadonlyVariable):
     def get(self):
         prefix = self.Get('cl_builder_path')
         version = self.Get('cl_builder_kernel_ver')
+        if not prefix:
+            return ""
         obj_file = max_default(
             self.filter(self.list(prefix), version=version),
             key=path.getmtime,