diff --git a/pandas/core/internals/array_manager.py b/pandas/core/internals/array_manager.py
index 407e16e1fa187..0925f3a3cee1f 100644
--- a/pandas/core/internals/array_manager.py
+++ b/pandas/core/internals/array_manager.py
@@ -834,7 +834,7 @@ def iset(
 
         # multiple columns -> convert slice or array to integer indices
         elif isinstance(loc, slice):
-            indices = range(
+            indices: range | np.ndarray = range(
                 loc.start if loc.start is not None else 0,
                 loc.stop if loc.stop is not None else self.shape_proper[1],
                 loc.step if loc.step is not None else 1,
@@ -842,9 +842,7 @@ def iset(
         else:
             assert isinstance(loc, np.ndarray)
             assert loc.dtype == "bool"
-            # error: Incompatible types in assignment (expression has type "ndarray",
-            # variable has type "range")
-            indices = np.nonzero(loc)[0]  # type: ignore[assignment]
+            indices = np.nonzero(loc)[0]
 
         assert value.ndim == 2
         assert value.shape[0] == len(self._axes[0])