diff --git a/util/dvsim/utils.py b/util/dvsim/utils.py
index cb4ad2b..dd2cce2 100644
--- a/util/dvsim/utils.py
+++ b/util/dvsim/utils.py
@@ -165,7 +165,7 @@
             # command and we're done.
             cmd_matches = list(wildcard_re.finditer(cmd))
             if not cmd_matches:
-                var = var[:idx] + run_cmd(cmd)
+                var = var[:match.start()] + run_cmd(cmd)
                 continue
 
             # Otherwise, check that each of them is ignored, or that