diff --git src/wp-includes/query.php src/wp-includes/query.php
index a31bf87..f9bdd0f 100644
--- src/wp-includes/query.php
+++ src/wp-includes/query.php
@@ -1574,8 +1574,9 @@ class WP_Query {
 		if ( '' !== $qv['menu_order'] ) $qv['menu_order'] = absint($qv['menu_order']);
 
 		// Fairly insane upper bound for search string lengths.
-		if ( ! empty( $qv['s'] ) && strlen( $qv['s'] ) > 1600 )
+		if ( ! is_scalar( $qv['s'] ) || ( ! empty( $qv['s'] ) && strlen( $qv['s'] ) > 1600 ) ) {
 			$qv['s'] = '';
+		}
 
 		// Compat. Map subpost to attachment.
 		if ( '' != $qv['subpost'] )
diff --git tests/phpunit/tests/query/parseQuery.php tests/phpunit/tests/query/parseQuery.php
new file mode 100644
index 0000000..c4cb1dd
--- /dev/null
+++ tests/phpunit/tests/query/parseQuery.php
@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * @group query
+ */
+class Tests_Query_ParseQuery extends WP_UnitTestCase {
+	/**
+	 * @ticket 29736
+	 */
+	public function test_parse_query_s_array() {
+		$q = new WP_Query();
+		$q->parse_query( array(
+			's' => array( 'foo' ),
+		) );
+
+		$this->assertSame( '', $q->query_vars['s'] );
+	}
+
+	public function test_parse_query_s_string() {
+		$q = new WP_Query();
+		$q->parse_query( array(
+			's' => 'foo',
+		) );
+
+		$this->assertSame( 'foo', $q->query_vars['s'] );
+	}
+
+	public function test_parse_query_s_float() {
+		$q = new WP_Query();
+		$q->parse_query( array(
+			's' => 3.5,
+		) );
+
+		$this->assertSame( 3.5, $q->query_vars['s'] );
+	}
+
+	public function test_parse_query_s_int() {
+		$q = new WP_Query();
+		$q->parse_query( array(
+			's' => 3,
+		) );
+
+		$this->assertSame( 3, $q->query_vars['s'] );
+	}
+
+	public function test_parse_query_s_bool() {
+		$q = new WP_Query();
+		$q->parse_query( array(
+			's' => true,
+		) );
+
+		$this->assertSame( true, $q->query_vars['s'] );
+	}
+}