diff --git a/fpdf.go b/fpdf.go
index de48ba7..ce07961 100644
--- a/fpdf.go
+++ b/fpdf.go
@@ -3489,8 +3489,8 @@ func (f *Fpdf) getpagesizestr(sizeStr string) (size SizeType) {
 	if strings.Contains(sizeStr, "x") {
 
 		var (
-			aString []string
-			aFloat  []float64
+			aString [2]string
+			aFloat  [2]float64
 			aErr    error
 		)
 		aString = strings.SplitN(sizeStr, "x", 2)