diff --git a/lib/compat/wordpress-5.9/theme.json b/lib/compat/wordpress-5.9/theme.json
index abb6db078d828a..ec29439d7f13f2 100644
--- a/lib/compat/wordpress-5.9/theme.json
+++ b/lib/compat/wordpress-5.9/theme.json
@@ -199,11 +199,6 @@
 					"slug": "small",
 					"size": "13px"
 				},
-				{
-					"name": "Normal",
-					"slug": "normal",
-					"size": "16px"
-				},
 				{
 					"name": "Medium",
 					"slug": "medium",
@@ -215,8 +210,8 @@
 					"size": "36px"
 				},
 				{
-					"name": "Huge",
-					"slug": "huge",
+					"name": "Extra Large",
+					"slug": "x-large",
 					"size": "42px"
 				}
 			],
diff --git a/packages/block-library/src/common.scss b/packages/block-library/src/common.scss
index 4111181e551133..46b2cd7b3b559e 100644
--- a/packages/block-library/src/common.scss
+++ b/packages/block-library/src/common.scss
@@ -6,6 +6,10 @@
 	@include background-colors-deprecated();
 	@include foreground-colors-deprecated();
 	@include gradient-colors-deprecated();
+	// This CSS Custom Properties aren't used anymore as defaults,
+	// but we still need to keep them for backward compatibility.
+	--wp--preset--font-size--normal: 16px;
+	--wp--preset--font-size--huge: 42px;
 }
 
 // Font sizes (not used now, kept because of backward compatibility).
@@ -17,6 +21,14 @@
 	font-size: 2.625em;
 }
 
+.has-normal-font-size {
+	font-size: var(--wp--preset--font-size--normal) !important;
+}
+
+.has-huge-font-size {
+	font-size: var(--wp--preset--font-size--huge) !important;
+}
+
 // Text alignments.
 .has-text-align-center {
 	text-align: center;
diff --git a/packages/block-library/src/editor.scss b/packages/block-library/src/editor.scss
index 29e905b79844bb..0dea452327cd2f 100644
--- a/packages/block-library/src/editor.scss
+++ b/packages/block-library/src/editor.scss
@@ -50,6 +50,10 @@
 	@include background-colors-deprecated();
 	@include foreground-colors-deprecated();
 	@include gradient-colors-deprecated();
+	// This CSS Custom Properties aren't used anymore as defaults,
+	// but we still need to keep them for backward compatibility.
+	--wp--preset--font-size--normal: 16px;
+	--wp--preset--font-size--huge: 42px;
 }
 
 // Font sizes (not used now, kept because of backward compatibility).
@@ -64,6 +68,14 @@
 	font-size: 42px;
 }
 
+.editor-styles-wrapper .has-normal-font-size {
+	font-size: var(--wp--preset--font-size--normal) !important;
+}
+
+.editor-styles-wrapper .has-huge-font-size {
+	font-size: var(--wp--preset--font-size--huge) !important;
+}
+
 /**
  * Editor Normalization Styles
  *