diff --git a/filter.go b/filter.go
index 7eae310f..3858a286 100644
--- a/filter.go
+++ b/filter.go
@@ -82,7 +82,10 @@ func CompileFilter(filter string) (*ber.Packet, error) {
 	if err != nil {
 		return nil, err
 	}
-	if pos != len(filter) {
+	switch {
+	case pos > len(filter):
+		return nil, NewError(ErrorFilterCompile, errors.New("ldap: unexpected end of filter"))
+	case pos < len(filter):
 		return nil, NewError(ErrorFilterCompile, errors.New("ldap: finished compiling filter with extra at end: "+fmt.Sprint(filter[pos:])))
 	}
 	return packet, nil
diff --git a/filter_test.go b/filter_test.go
index ae1b79b0..2b019ac5 100644
--- a/filter_test.go
+++ b/filter_test.go
@@ -131,6 +131,12 @@ var testFilters = []compileTest{
 		expectedType:   0,
 		expectedErr:    "unexpected end of filter",
 	},
+	compileTest{
+		filterStr:      `((cn=)`,
+		expectedFilter: ``,
+		expectedType:   0,
+		expectedErr:    "unexpected end of filter",
+	},
 	compileTest{
 		filterStr:      `(&(objectclass=inetorgperson)(cn=中文))`,
 		expectedFilter: `(&(objectclass=inetorgperson)(cn=\e4\b8\ad\e6\96\87))`,