diff --git a/lib/galaxy/schema/schema.py b/lib/galaxy/schema/schema.py
index 85314827275..277bb82f481 100644
--- a/lib/galaxy/schema/schema.py
+++ b/lib/galaxy/schema/schema.py
@@ -66,7 +66,7 @@ IMPLICIT_COLLECTION_JOBS_MODEL_CLASS = Literal["ImplicitCollectionJobs"]
 
 OptionalNumberT = Annotated[Optional[Union[int, float]], Field(None)]
 
-TAG_ITEM_PATTERN = r"^([^\s.:])+(.[^\s.:]+)*(:[^\s.:]+)?$"
+TAG_ITEM_PATTERN = r"^([^\s.:])+(\.[^\s.:]+)*(:\S+)?$"
 
 
 class DatasetState(str, Enum):