diff --git a/filter.go b/filter.go
index 9c30615..4cdf61b 100644
--- a/filter.go
+++ b/filter.go
@@ -4,6 +4,8 @@
 
 package mop
 
+import "strings"
+
 // Filter gets called to sort stock quotes by one of the columns. The
 // setup is rather lengthy; there should probably be more concise way
 // that uses reflection and avoids hardcoding the column names.