diff --git a/src/wp-includes/class-wp-roles.php b/src/wp-includes/class-wp-roles.php
index 2cb9cdfe95296..c1ecb2824e7f1 100644
--- a/src/wp-includes/class-wp-roles.php
+++ b/src/wp-includes/class-wp-roles.php
@@ -307,7 +307,13 @@ public function init_roles() {
 		$this->role_objects = array();
 		$this->role_names   = array();
 		foreach ( array_keys( $this->roles ) as $role ) {
-			$this->role_objects[ $role ] = new WP_Role( $role, $this->roles[ $role ]['capabilities'] );
+			$role_capabilities = $this->roles[ $role ]['capabilities'] ?? array();
+
+			if ( ! is_array( $role_capabilities ) ) {
+				$role_capabilities = array();
+			}
+
+			$this->role_objects[ $role ] = new WP_Role( $role, $role_capabilities );
 			$this->role_names[ $role ]   = $this->roles[ $role ]['name'];
 		}
 
diff --git a/src/wp-includes/class-wp-user-query.php b/src/wp-includes/class-wp-user-query.php
index 3815023924489..3fe7feb6a29fd 100644
--- a/src/wp-includes/class-wp-user-query.php
+++ b/src/wp-includes/class-wp-user-query.php
@@ -482,7 +482,10 @@ public function prepare_query( $query = array() ) {
 		$caps_with_roles = array();
 
 		foreach ( $available_roles as $role => $role_data ) {
-			$role_caps = array_keys( array_filter( $role_data['capabilities'] ) );
+			$role_capabilities = $role_data['capabilities'] ?? array();
+			$role_caps         = is_array( $role_capabilities )
+				? array_keys( array_filter( $role_capabilities ) )
+				: array();
 
 			foreach ( $capabilities as $cap ) {
 				if ( in_array( $cap, $role_caps, true ) ) {
diff --git a/tests/phpunit/tests/user/query.php b/tests/phpunit/tests/user/query.php
index 5978f4bf55e58..50e9ef4973413 100644
--- a/tests/phpunit/tests/user/query.php
+++ b/tests/phpunit/tests/user/query.php
@@ -1959,6 +1959,53 @@ public function test_capability__in_capability__not_in_combined() {
 		}
 	}
 
+	/**
+	 * A role stored without a 'capabilities' key (for example, left behind by a
+	 * deactivated plugin) should be skipped rather than causing a fatal error.
+	 *
+	 * @ticket 62600
+	 */
+	public function test_capability_query_with_role_missing_capabilities_key() {
+		global $wp_roles;
+
+		$wp_roles->add_role( 'role_missing_caps', 'Role Missing Caps' );
+
+		$roles = get_option( $wp_roles->role_key );
+		unset( $roles['role_missing_caps']['capabilities'] );
+		update_option( $wp_roles->role_key, $roles );
+
+		$wp_user_search = new WP_User_Query( array( 'capability' => 'read' ) );
+		$users          = $wp_user_search->get_results();
+
+		$this->assertNotEmpty( $users );
+
+		$wp_roles->remove_role( 'role_missing_caps' );
+	}
+
+	/**
+	 * A role whose 'capabilities' value isn't an array should be skipped rather
+	 * than causing a fatal error, the same as a missing key.
+	 *
+	 * @ticket 62600
+	 */
+	public function test_capability_query_with_role_capabilities_not_an_array() {
+		global $wp_roles;
+
+		$wp_roles->add_role( 'role_invalid_caps', 'Role Invalid Caps' );
+
+		$roles = get_option( $wp_roles->role_key );
+
+		$roles['role_invalid_caps']['capabilities'] = false;
+		update_option( $wp_roles->role_key, $roles );
+
+		$wp_user_search = new WP_User_Query( array( 'capability' => 'read' ) );
+		$users          = $wp_user_search->get_results();
+
+		$this->assertNotEmpty( $users );
+
+		$wp_roles->remove_role( 'role_invalid_caps' );
+	}
+
 	/**
 	 * @ticket 16841
 	 * @group ms-required