diff --git a/src/PairedRouting.php b/src/PairedRouting.php
index 20c52720720..049b889ff24 100644
--- a/src/PairedRouting.php
+++ b/src/PairedRouting.php
@@ -391,13 +391,16 @@ public function detect_endpoint_in_environment() {
 				continue;
 			}
 
+			$paired_url_structure = $this->get_paired_url_structure();
+
 			// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
 			$old_path = wp_unslash( $_SERVER[ $var_name ] ); // Because of wp_magic_quotes().
-			$new_path = $this->get_paired_url_structure()->remove_endpoint( $old_path );
-			if ( $old_path === $new_path ) {
+			if ( ! $paired_url_structure->has_endpoint( $old_path ) ) {
 				continue;
 			}
 
+			$new_path = $paired_url_structure->remove_endpoint( $old_path );
+
 			$this->suspended_environment_variables[ $var_name ] = [ $old_path, $new_path ];
 
 			$this->did_request_endpoint = true;
diff --git a/tests/php/src/PairedRoutingTest.php b/tests/php/src/PairedRoutingTest.php
index 8abdf79742f..42e8d94dcd5 100644
--- a/tests/php/src/PairedRoutingTest.php
+++ b/tests/php/src/PairedRoutingTest.php
@@ -214,6 +214,12 @@ public function get_data_for_test_paired_requests() {
 				'/',
 				false,
 			],
+			'url_with_empty_query_var'              => [
+				AMP_Theme_Support::READER_MODE_SLUG,
+				Option::PAIRED_URL_STRUCTURE_QUERY_VAR,
+				'/?foo=',
+				false,
+			],
 			'path_suffix_transitional_mode_amp'     => [
 				AMP_Theme_Support::TRANSITIONAL_MODE_SLUG,
 				Option::PAIRED_URL_STRUCTURE_PATH_SUFFIX,
@@ -370,6 +376,10 @@ public function test_detect_endpoint_in_environment() {
 		$_SERVER['REQUEST_URI'] = $this->instance->add_endpoint( '/' );
 		$this->instance->detect_endpoint_in_environment();
 		$this->assertTrue( $this->get_private_property( $this->instance, 'did_request_endpoint' ) );
+
+		$_SERVER['REQUEST_URI'] = '/?foo=';
+		$this->instance->detect_endpoint_in_environment();
+		$this->assertFalse( $this->get_private_property( $this->instance, 'did_request_endpoint' ) );
 	}
 
 	/** @return array */