Fix

src/index.es6

@@ -61,15 +61,17 @@ function buildChildren( tokens, components ) {
 			break;
 		}
 		// componentSelfClosing token
-		children.push( components[ token.value ] );
+		if ( components[ token.value ] ) {
+			children.push( React.cloneElement( components[ token.value ], { key: i } ) );
+		}
 		continue;
 	}
 
 	if ( openComponent ) {
 		closeIndex = getCloseIndex( openIndex, tokens );
 		grandChildTokens = tokens.slice( ( openIndex + 1 ), closeIndex );
 		grandChildren = buildChildren( grandChildTokens, components );
-		clonedOpenComponent = React.cloneElement( openComponent, {}, grandChildren );
+		clonedOpenComponent = React.cloneElement( openComponent, { key: openIndex }, grandChildren );
 		children.push( clonedOpenComponent );
 
 		if ( closeIndex < tokens.length - 1 ) {
@@ -83,17 +85,7 @@ function buildChildren( tokens, components ) {
 		return children[ 0 ];
 	}
 
-	return children.map( ( child, index ) => {
-		if ( child ) {
-			return React.cloneElement(
-				child,
-				{ key: `interpolation-child-${ index }` },
-				child.props !== undefined
-					? child.props.children
-					: undefined
-			 );
-		}
-	} );
+	return children;
 }
 
 function interpolate( options ) {