diff --git a/fpdf.go b/fpdf.go
index e314199..60c04e9 100644
--- a/fpdf.go
+++ b/fpdf.go
@@ -3503,7 +3503,7 @@ func (f *Fpdf) getpagesizestr(sizeStr string) (size SizeType) {
 				f.err = fmt.Errorf("unknown page size %s", sizeStr)
 			}
 		}
-		size, ok = SizeType{aFloat[0] * f.k, aFloat[1] * f.k}, true
+		size, ok = SizeType{(aFloat[0] * f.k), (aFloat[1] * f.k)}, true
 	} else {
 		//20210302 archium addendum end
 		size, ok = f.stdPageSizes[sizeStr]