diff --git a/src/lightning/fabric/plugins/precision/amp.py b/src/lightning/fabric/plugins/precision/amp.py
index a7bf1113d1..d89ff1597e 100644
--- a/src/lightning/fabric/plugins/precision/amp.py
+++ b/src/lightning/fabric/plugins/precision/amp.py
@@ -56,7 +56,7 @@ class MixedPrecision(Precision):
                 if _TORCH_GREATER_EQUAL_2_4
                 else getattr(
                     torch,
-                    "cuda" if not isinstance(device, str) or device.split(":")[0] == "cpu" else device.split(":")[0],
+                    "cuda" if device.split(":")[0] == "cpu" else device.split(":")[0],
                 ).amp.GradScaler()
             )
         if scaler is not None and self.precision == "bf16-mixed":
diff --git a/src/lightning/pytorch/plugins/precision/amp.py b/src/lightning/pytorch/plugins/precision/amp.py
index d610057e2a..b6a6fd1277 100644
--- a/src/lightning/pytorch/plugins/precision/amp.py
+++ b/src/lightning/pytorch/plugins/precision/amp.py
@@ -56,7 +56,7 @@ class MixedPrecision(Precision):
                 if _TORCH_GREATER_EQUAL_2_4
                 else getattr(
                     torch,
-                    "cuda" if not isinstance(device, str) or device.split(":")[0] == "cpu" else device.split(":")[0],
+                    "cuda" if device.split(":")[0] == "cpu" else device.split(":")[0],
                 ).amp.GradScaler()
             )
         if scaler is not None and self.precision == "bf16-mixed":