diff --git a/filtering.go b/filtering.go
index 8b1897e..cf577dc 100644
--- a/filtering.go
+++ b/filtering.go
@@ -106,9 +106,9 @@ func MakeFilterString(prefix string, filters Filter, validFilters []string) (res
 
 		res += "("
 		for i, f := range filter {
-			if strings.HasPrefix(f, "<") || strings.HasPrefix(f, ">") {
+			if strings.HasPrefix(f, "<") || strings.HasPrefix(f, ">") || strings.HasPrefix(f, "!") {
 				symbol = string(f[0])
-				f = strings.TrimLeft(f, "<>")
+				f = strings.TrimLeft(f, "<>!")
 				if strings.HasPrefix(f, "=") {
 					f = strings.TrimLeft(f, "=")
 					symbol += "="