diff --git a/src/ApacheModRewriteGenerator.php b/src/ApacheModRewriteGenerator.php
index 1eeb2de..fd88773 100644
--- a/src/ApacheModRewriteGenerator.php
+++ b/src/ApacheModRewriteGenerator.php
@@ -42,7 +42,7 @@ public function generateRewrite( string $from, string $to, int $type ) : string
 
 		$output = '';
 
-		if( !$fromHost && $toHost ) {
+		if( $fromHost && !$toHost ) {
 			throw new AmbiguousRelativeHostException(
 				'Unclear relative host. When the "FROM" URI specifies a HOST the "TO" MUST specify a HOST as well.'
 			);