@@ -72,6 +72,34 @@ const styleSupportKeys = [
 const hasStyleSupport = ( nameOrType ) =>
 	styleSupportKeys.some( ( key ) => hasBlockSupport( nameOrType, key ) );
 
+/**
+ * Converts a CSS property name into the key a React style object expects.
+ *
+ * Vendor-prefixed properties are camelCased without their leading dash, so
+ * `-webkit-background-clip` becomes `WebkitBackgroundClip`.
+ *
+ * @param {string} key CSS property name.
+ *
+ * @return {string} React style object key.
+ */
+function getReactStyleKey( key ) {
+	// Custom properties start with two dashes. React writes them verbatim.
+	if ( ! key.startsWith( '-' ) || key.startsWith( '--' ) ) {
+		return key;
+	}
+
+	const camelCased = key
+		.slice( 1 )
+		.replace( /-([a-z])/g, ( _, character ) => character.toUpperCase() );
+
+	// `-ms-` is the one prefix React keeps lowercase, e.g. `msFlexAlign`.
+	return key.startsWith( '-ms-' )
+		? camelCased
+		: camelCased.replace( /^[a-z]/, ( character ) =>
+				character.toUpperCase()
+			);
+}
+
 /**
  * Returns the inline styles to add depending on the style object
  *
@@ -84,20 +112,7 @@ export function getInlineStyles( styles = {} ) {
 	// The goal is to move everything to server side generated engine styles
 	// This is temporary as we absorb more and more styles into the engine.
 	getCSSRules( styles ).forEach( ( rule ) => {
-		// Vendor-prefixed CSS properties start with a single dash (e.g.
-		// `-webkit-background-clip`). React style objects require camelCase
-		// keys without the leading dash (e.g. `WebkitBackgroundClip`), so
-		// convert those. Custom properties start with two and are passed
-		// through, since React writes them verbatim.
-		const isVendorPrefixed =
-			rule.key.startsWith( '-' ) && ! rule.key.startsWith( '--' );
-		const key = isVendorPrefixed
-			? rule.key
-					.slice( 1 )
-					.replace( /-([a-z])/g, ( _, c ) => c.toUpperCase() )
-					.replace( /^[a-z]/, ( c ) => c.toUpperCase() )
-			: rule.key;
-		output[ key ] = rule.value;
+		output[ getReactStyleKey( rule.key ) ] = rule.value;
 	} );
 
 	return output;