diff --git a/lib/font/subsetFont.go b/lib/font/subsetFont.go
index 32c74fe68..427283edb 100644
--- a/lib/font/subsetFont.go
+++ b/lib/font/subsetFont.go
@@ -369,7 +369,8 @@ func (utf *utf8FontFile) generateCMAPTable(cidSymbolPairCollection map[int]int,
 	cmap = append(cmap, 0)
 
 	// Calculating cmap length based off of fpdf https://github.com/Setasign/FPDF/blob/f4104a04c9a3f95c4c26a0a0531abebcc980987a/makefont/ttfparser.php#L476
-	data = append(data, 6+len(cmap)*2, 0) // [version, numTables, platformID, encodingID, offset, format], length, language
+	length := (3 + len(cmap)) * 2  // the 3 extra bytes are for encodingID, offset, format, which are part of the cmap length
+	data = append(data, length, 0) // [version, numTables, platformID, encodingID, offset, format], length, language
 	data = append(data, cmap...)
 
 	cmapstr := make([]byte, 0)