diff --git a/lib/bb/parse/ast.py b/lib/bb/parse/ast.py
index 49a0788038..317f00d3bd 100644
--- a/lib/bb/parse/ast.py
+++ b/lib/bb/parse/ast.py
@@ -371,7 +371,10 @@ class AddFragmentsNode(AstNode):
         fragments = data.getVar(self.fragments_variable)
         layers = data.getVar('BBLAYERS')
         flagged_variables = data.getVar(self.flagged_variables_list_variable).split()
-        builtin_fragments = {f[0]:f[1] for f in [f.split(':') for f in data.getVar(self.builtin_fragments_variable).split()] }
+        builtin_fragments = {}
+        builtin_fragments_var = data.getVar(self.builtin_fragments_variable)
+        if builtin_fragments_var is not None:
+            builtin_fragments = {f[0]:f[1] for f in [f.split(':') for f in builtin_fragments_var.split()]}
 
         if not fragments:
             return