diff --git a/project.example.yml b/project.example.yml
index e4498da..61beb75 100644
--- a/project.example.yml
+++ b/project.example.yml
@@ -56,3 +56,6 @@ tool_options:
     - "3"
 
   fuse: []
+
+  isim: 
+    - "-gui"
\ No newline at end of file
diff --git a/src/hdlbuild/models/project.py b/src/hdlbuild/models/project.py
index 20415e3..4d75853 100644
--- a/src/hdlbuild/models/project.py
+++ b/src/hdlbuild/models/project.py
@@ -14,6 +14,7 @@ class ToolOptions(BaseModel):
     bitgen: List[str] = Field(default_factory=list)
     trace: List[str] = Field(default_factory=list)
     fuse: List[str] = Field(default_factory=list)
+    isim: List[str] = Field(default_factory=list)
 
 class Dependency(BaseModel):
     name: Optional[str] = None  # Name ist jetzt optional