diff --git a/src/wp-admin/includes/class-wp-filesystem-direct.php b/src/wp-admin/includes/class-wp-filesystem-direct.php
index 7551e3d273..17ccad8d5d 100644
--- a/src/wp-admin/includes/class-wp-filesystem-direct.php
+++ b/src/wp-admin/includes/class-wp-filesystem-direct.php
@@ -223,6 +223,9 @@ class WP_Filesystem_Direct extends WP_Filesystem_Base {
 			return $owneruid;
 		}
 		$ownerarray = posix_getpwuid( $owneruid );
+		if ( ! $ownerarray ) {
+			return false;
+		}
 		return $ownerarray['name'];
 	}
 
@@ -257,6 +260,9 @@ class WP_Filesystem_Direct extends WP_Filesystem_Base {
 			return $gid;
 		}
 		$grouparray = posix_getgrgid( $gid );
+		if ( ! $grouparray ) {
+			return false;
+		}
 		return $grouparray['name'];
 	}
 
diff --git a/src/wp-admin/includes/class-wp-filesystem-ssh2.php b/src/wp-admin/includes/class-wp-filesystem-ssh2.php
index c099259e1f..94853a650b 100644
--- a/src/wp-admin/includes/class-wp-filesystem-ssh2.php
+++ b/src/wp-admin/includes/class-wp-filesystem-ssh2.php
@@ -402,6 +402,9 @@ class WP_Filesystem_SSH2 extends WP_Filesystem_Base {
 			return $owneruid;
 		}
 		$ownerarray = posix_getpwuid( $owneruid );
+		if ( ! $ownerarray ) {
+			return false;
+		}
 		return $ownerarray['name'];
 	}
 
@@ -434,6 +437,9 @@ class WP_Filesystem_SSH2 extends WP_Filesystem_Base {
 			return $gid;
 		}
 		$grouparray = posix_getgrgid( $gid );
+		if ( ! $grouparray ) {
+			return false;
+		}
 		return $grouparray['name'];
 	}