Index: wp-includes/blocks/buttons/style-rtl.css
===================================================================
--- wp-includes/blocks/buttons/style-rtl.css	(revision 53284)
+++ wp-includes/blocks/buttons/style-rtl.css	(working copy)
@@ -120,7 +120,14 @@
   margin-left: auto;
   width: 100%;
 }
-
+.wp-block-buttons:not(.is-content-justification-space-between,
+.is-content-justification-right,
+.is-content-justification-left,
+.is-content-justification-center) .wp-block-button.alignright {
+  /* stylelint-enable indentation */
+  width: 100%;
+  text-align: right;
+}
 .wp-block-button.aligncenter {
   text-align: center;
 }
\ No newline at end of file
Index: wp-includes/blocks/buttons/style-rtl.min.css
===================================================================
--- wp-includes/blocks/buttons/style-rtl.min.css	(revision 53284)
+++ wp-includes/blocks/buttons/style-rtl.min.css	(working copy)
@@ -1 +1,9 @@
-.wp-block-buttons.is-vertical{flex-direction:column}.wp-block-buttons.is-vertical>.wp-block-button:last-child{margin-bottom:0}.wp-block-buttons>.wp-block-button{display:inline-block;margin:0}.wp-block-buttons.is-content-justification-left{justify-content:flex-start}.wp-block-buttons.is-content-justification-left.is-vertical{align-items:flex-start}.wp-block-buttons.is-content-justification-center{justify-content:center}.wp-block-buttons.is-content-justification-center.is-vertical{align-items:center}.wp-block-buttons.is-content-justification-right{justify-content:flex-end}.wp-block-buttons.is-content-justification-right.is-vertical{align-items:flex-end}.wp-block-buttons.is-content-justification-space-between{justify-content:space-between}.wp-block-buttons.aligncenter{text-align:center}.wp-block-buttons:not(.is-content-justification-space-between,.is-content-justification-right,.is-content-justification-left,.is-content-justification-center) .wp-block-button.aligncenter{margin-right:auto;margin-left:auto;width:100%}.wp-block-button.aligncenter{text-align:center}
\ No newline at end of file
+.wp-block-buttons.is-vertical{flex-direction:column}.wp-block-buttons.is-vertical>.wp-block-button:last-child{margin-bottom:0}.wp-block-buttons>.wp-block-button{display:inline-block;margin:0}.wp-block-buttons.is-content-justification-left{justify-content:flex-start}.wp-block-buttons.is-content-justification-left.is-vertical{align-items:flex-start}.wp-block-buttons.is-content-justification-center{justify-content:center}.wp-block-buttons.is-content-justification-center.is-vertical{align-items:center}.wp-block-buttons.is-content-justification-right{justify-content:flex-end}.wp-block-buttons.is-content-justification-right.is-vertical{align-items:flex-end}.wp-block-buttons.is-content-justification-space-between{justify-content:space-between}.wp-block-buttons.aligncenter{text-align:center}.wp-block-buttons:not(.is-content-justification-space-between,.is-content-justification-right,.is-content-justification-left,.is-content-justification-center) .wp-block-button.aligncenter{margin-right:auto;margin-left:auto;width:100%}.wp-block-button.aligncenter{text-align:center}
+.wp-block-buttons:not(.is-content-justification-space-between,
+.is-content-justification-right,
+.is-content-justification-left,
+.is-content-justification-center) .wp-block-button.alignright {
+  /* stylelint-enable indentation */
+  width: 100%;
+  text-align: right;
+}
\ No newline at end of file
Index: wp-includes/blocks/buttons/style.css
===================================================================
--- wp-includes/blocks/buttons/style.css	(revision 53284)
+++ wp-includes/blocks/buttons/style.css	(working copy)
@@ -120,7 +120,14 @@
   margin-right: auto;
   width: 100%;
 }
-
+.wp-block-buttons:not(.is-content-justification-space-between,
+.is-content-justification-right,
+.is-content-justification-left,
+.is-content-justification-center) .wp-block-button.alignright {
+  /* stylelint-enable indentation */
+  width: 100%;
+  text-align: right;
+}
 .wp-block-button.aligncenter {
   text-align: center;
 }
\ No newline at end of file
Index: wp-includes/blocks/buttons/style.min.css
===================================================================
--- wp-includes/blocks/buttons/style.min.css	(revision 53284)
+++ wp-includes/blocks/buttons/style.min.css	(working copy)
@@ -1 +1,9 @@
-.wp-block-buttons.is-vertical{flex-direction:column}.wp-block-buttons.is-vertical>.wp-block-button:last-child{margin-bottom:0}.wp-block-buttons>.wp-block-button{display:inline-block;margin:0}.wp-block-buttons.is-content-justification-left{justify-content:flex-start}.wp-block-buttons.is-content-justification-left.is-vertical{align-items:flex-start}.wp-block-buttons.is-content-justification-center{justify-content:center}.wp-block-buttons.is-content-justification-center.is-vertical{align-items:center}.wp-block-buttons.is-content-justification-right{justify-content:flex-end}.wp-block-buttons.is-content-justification-right.is-vertical{align-items:flex-end}.wp-block-buttons.is-content-justification-space-between{justify-content:space-between}.wp-block-buttons.aligncenter{text-align:center}.wp-block-buttons:not(.is-content-justification-space-between,.is-content-justification-right,.is-content-justification-left,.is-content-justification-center) .wp-block-button.aligncenter{margin-left:auto;margin-right:auto;width:100%}.wp-block-button.aligncenter{text-align:center}
\ No newline at end of file
+.wp-block-buttons.is-vertical{flex-direction:column}.wp-block-buttons.is-vertical>.wp-block-button:last-child{margin-bottom:0}.wp-block-buttons>.wp-block-button{display:inline-block;margin:0}.wp-block-buttons.is-content-justification-left{justify-content:flex-start}.wp-block-buttons.is-content-justification-left.is-vertical{align-items:flex-start}.wp-block-buttons.is-content-justification-center{justify-content:center}.wp-block-buttons.is-content-justification-center.is-vertical{align-items:center}.wp-block-buttons.is-content-justification-right{justify-content:flex-end}.wp-block-buttons.is-content-justification-right.is-vertical{align-items:flex-end}.wp-block-buttons.is-content-justification-space-between{justify-content:space-between}.wp-block-buttons.aligncenter{text-align:center}.wp-block-buttons:not(.is-content-justification-space-between,.is-content-justification-right,.is-content-justification-left,.is-content-justification-center) .wp-block-button.aligncenter{margin-left:auto;margin-right:auto;width:100%}.wp-block-button.aligncenter{text-align:center}
+.wp-block-buttons:not(.is-content-justification-space-between,
+.is-content-justification-right,
+.is-content-justification-left,
+.is-content-justification-center) .wp-block-button.alignright {
+  /* stylelint-enable indentation */
+  width: 100%;
+  text-align: right;
+}