diff --git a/src/options.go b/src/options.go
index 38558771..a99ab0b6 100644
--- a/src/options.go
+++ b/src/options.go
@@ -995,7 +995,7 @@ func parsePreviewWindow(opts *previewOpts, input string) {
 	opts.wrap = false
 
 	tokens := strings.Split(input, ":")
-	sizeRegex := regexp.MustCompile("^[1-9][0-9]*%?$")
+	sizeRegex := regexp.MustCompile("^[0-9]+%?$")
 	offsetRegex := regexp.MustCompile("^\\+([0-9]+|{-?[0-9]+})(-[0-9]+|-/[1-9][0-9]*)?$")
 	for _, token := range tokens {
 		switch token {
diff --git a/src/terminal.go b/src/terminal.go
index b683c459..2208cf47 100644
--- a/src/terminal.go
+++ b/src/terminal.go
@@ -1697,10 +1697,11 @@ func (t *Terminal) Loop() {
 				// We don't display preview window if no match
 				if items[0] != nil {
 					command := t.replacePlaceholder(commandTemplate, false, string(t.Input()), items)
-					height := t.pwindow.Height()
-					offset := t.evaluateScrollOffset(items, height)
+					offset := 0
 					cmd := util.ExecCommand(command, true)
 					if t.pwindow != nil {
+						height := t.pwindow.Height()
+						offset = t.evaluateScrollOffset(items, height)
 						env := os.Environ()
 						lines := fmt.Sprintf("LINES=%d", height)
 						columns := fmt.Sprintf("COLUMNS=%d", t.pwindow.Width())