diff --git a/xarray/core/dataset.py b/xarray/core/dataset.py
index 6ecd9b59f8e..2d15ff586e4 100644
--- a/xarray/core/dataset.py
+++ b/xarray/core/dataset.py
@@ -3550,7 +3550,7 @@ def update(self, other: "CoercibleMapping", inplace: bool = None) -> "Dataset":
 
     def merge(
         self,
-        other: "CoercibleMapping",
+        other: Union["CoercibleMapping", "DataArray"],
         inplace: bool = None,
         overwrite_vars: Union[Hashable, Iterable[Hashable]] = frozenset(),
         compat: str = "no_conflicts",