diff --git a/snakemake/rules.py b/snakemake/rules.py
index 39b05e27b..d922ef012 100644
--- a/snakemake/rules.py
+++ b/snakemake/rules.py
@@ -708,7 +708,7 @@ def apply_input_function(
             # Function evaluation can depend on input files. Since expansion can happen during dryrun,
             # where input files are not yet present, we need to skip such cases and
             # mark them as <TBD>.
-            if e.filename in aux_params["input"]:
+            if "input" in aux_params and e.filename in aux_params["input"]:
                 value = TBDString()
             else:
                 raise e