diff --git a/builder/amazon/chroot/block_device.go b/builder/amazon/chroot/block_device.go
index 3e789d258..78bc784c4 100644
--- a/builder/amazon/chroot/block_device.go
+++ b/builder/amazon/chroot/block_device.go
@@ -55,7 +55,8 @@ func (b *BlockDevice) Prepare(ctx *interpolate.Context) error {
 			"true` when setting a kms_key_id.", b.DeviceName)
 	}
 
-	return nil
+	_, err = interpolate.RenderInterface(&b, ctx)
+	return err
 }
 
 func (bds BlockDevices) Prepare(ctx *interpolate.Context) (errs []error) {
diff --git a/builder/amazon/common/block_device.go b/builder/amazon/common/block_device.go
index eade27637..c0acc8224 100644
--- a/builder/amazon/common/block_device.go
+++ b/builder/amazon/common/block_device.go
@@ -133,7 +133,8 @@ func (b *BlockDevice) Prepare(ctx *interpolate.Context) error {
 			"true` when setting a kms_key_id.", b.DeviceName)
 	}
 
-	return nil
+	_, err := interpolate.RenderInterface(&b, ctx)
+	return err
 }
 
 func (bds BlockDevices) Prepare(ctx *interpolate.Context) (errs []error) {