diff --git a/pyiron_workflow/mixin/preview.py b/pyiron_workflow/mixin/preview.py
index 41dc8417..d8e71238 100644
--- a/pyiron_workflow/mixin/preview.py
+++ b/pyiron_workflow/mixin/preview.py
@@ -75,7 +75,7 @@ def preview_outputs(cls) -> dict[str, Any]:
         return cls._build_outputs_preview()
 
     @classmethod
-    def preview_io(cls) -> DotDict[str:dict]:
+    def preview_io(cls) -> DotDict[str, dict]:
         return DotDict(
             {"inputs": cls.preview_inputs(), "outputs": cls.preview_outputs()}
         )
diff --git a/pyiron_workflow/mixin/semantics.py b/pyiron_workflow/mixin/semantics.py
index 1a3a805c..7ce756ba 100644
--- a/pyiron_workflow/mixin/semantics.py
+++ b/pyiron_workflow/mixin/semantics.py
@@ -188,7 +188,7 @@ def __init__(
         super().__init__(*args, label=label, parent=parent, **kwargs)
 
     @property
-    def children(self) -> bidict[str:Semantic]:
+    def children(self) -> bidict[str, Semantic]:
         return self._children
 
     @property