diff --git a/tools_webrtc/autoroller/roll_deps.py b/tools_webrtc/autoroller/roll_deps.py
index 77dd7d8d73..4a505b5b7b 100755
--- a/tools_webrtc/autoroller/roll_deps.py
+++ b/tools_webrtc/autoroller/roll_deps.py
@@ -97,6 +97,10 @@ class RollError(Exception):
   pass
 
 
+def StrExpansion():
+  return lambda str_value: str_value
+
+
 def VarLookup(local_scope):
   return lambda var_name: local_scope['vars'][var_name]
 
@@ -104,6 +108,7 @@ def VarLookup(local_scope):
 def ParseDepsDict(deps_content):
   local_scope = {}
   global_scope = {
+    'Str': StrExpansion(),
     'Var': VarLookup(local_scope),
     'deps_os': {},
   }