diff --git a/edalize/tools/vcs.py b/edalize/tools/vcs.py
index b5d8fd4e..ec0339e7 100644
--- a/edalize/tools/vcs.py
+++ b/edalize/tools/vcs.py
@@ -273,7 +273,7 @@ def write_config_files(self):
         s = ""
         for key, value in _parameters.items():
             _value = self._param_value_str(value, '"')
-            s += f"assign {_value} {key}\n"
+            s += f"assign {_value} {self.toplevel}.{key}\n"
         self.update_config_file("parameters.txt", s)
 
     def run(self):
diff --git a/tests/tools/vcs/2stage_basic/parameters.txt b/tests/tools/vcs/2stage_basic/parameters.txt
index 9363f77f..dcadfe36 100644
--- a/tests/tools/vcs/2stage_basic/parameters.txt
+++ b/tests/tools/vcs/2stage_basic/parameters.txt
@@ -1,3 +1,3 @@
-assign 1 vlogparam_bool
-assign 42 vlogparam_int
-assign "hello" vlogparam_str
+assign 1 top_module.vlogparam_bool
+assign 42 top_module.vlogparam_int
+assign "hello" top_module.vlogparam_str
diff --git a/tests/tools/vcs/basic/parameters.txt b/tests/tools/vcs/basic/parameters.txt
index 9363f77f..dcadfe36 100644
--- a/tests/tools/vcs/basic/parameters.txt
+++ b/tests/tools/vcs/basic/parameters.txt
@@ -1,3 +1,3 @@
-assign 1 vlogparam_bool
-assign 42 vlogparam_int
-assign "hello" vlogparam_str
+assign 1 top_module.vlogparam_bool
+assign 42 top_module.vlogparam_int
+assign "hello" top_module.vlogparam_str