diff --git a/includes/class-wc-coupon.php b/includes/class-wc-coupon.php
index 276884710a8..12bb0253acc 100644
--- a/includes/class-wc-coupon.php
+++ b/includes/class-wc-coupon.php
@@ -271,13 +271,15 @@ class WC_Coupon {
 			$this->usage_count--;
 			update_post_meta( $this->id, 'usage_count', $this->usage_count );
 
-			/**
-			 * We're doing this the long way because `delete_post_meta( $id, $key, $value )` deletes
-			 * all instances where the key and value match, and we only want to delete one.
-			 */
-			$meta_id = $wpdb->get_var( $wpdb->prepare( "SELECT meta_id FROM $wpdb->postmeta WHERE meta_key = '_used_by' AND meta_value = %s AND post_id = %d LIMIT 1;", $used_by, $this->id ) );
-			if ( $meta_id ) {
-				delete_metadata_by_mid( 'post', $meta_id );
+			if ( $used_by ) {
+				/**
+				 * We're doing this the long way because `delete_post_meta( $id, $key, $value )` deletes
+				 * all instances where the key and value match, and we only want to delete one.
+				 */
+				$meta_id = $wpdb->get_var( $wpdb->prepare( "SELECT meta_id FROM $wpdb->postmeta WHERE meta_key = '_used_by' AND meta_value = %s AND post_id = %d LIMIT 1;", $used_by, $this->id ) );
+				if ( $meta_id ) {
+					delete_metadata_by_mid( 'post', $meta_id );
+				}
 			}
 		}
 	}