diff --git a/packages/block-library/src/spacer/edit.js b/packages/block-library/src/spacer/edit.js
index 1e0ffb9700d685..7571c7e25d5475 100644
--- a/packages/block-library/src/spacer/edit.js
+++ b/packages/block-library/src/spacer/edit.js
@@ -299,7 +299,8 @@ const SpacerEdit = ( {
 			}
 		} else if (
 			isFlexLayout &&
-			( selfStretch === 'fill' || selfStretch === 'fit' )
+			( selfStretch === 'fill' || selfStretch === 'fit' ) &&
+			width !== undefined
 		) {
 			if ( inheritedOrientation === 'horizontal' ) {
 				setAttributes( {