diff --git a/R/read.px.R b/R/read.px.R
index 9be8bc1..e8cc2e0 100644
--- a/R/read.px.R
+++ b/R/read.px.R
@@ -31,7 +31,7 @@
 #################################################################
 
 read.px <- function(filename, encoding = NULL, 
-                    na.strings = c('"."', '".."', '"..."', '"...."', '":"')) {
+                    na.strings = c('"."', '".."', '"..."', '"...."', '"....."', '"......"', '":"')) {
 
     ## auxiliary functions ##
 
diff --git a/man/read.px.Rd b/man/read.px.Rd
index 0e6d1d7..aa257ae 100644
--- a/man/read.px.Rd
+++ b/man/read.px.Rd
@@ -8,7 +8,7 @@ This function reads a PC-AXIS file (a text file with certain format) and creates
 }
 \usage{
 read.px(filename, encoding = NULL, 
-        na.strings = c('"."', '".."', '"..."', '"...."', '":"'))
+        na.strings = c('"."', '".."', '"..."', '"...."', '"....."', '"......"', '":"'))
 }
 
 \arguments{
@@ -23,7 +23,7 @@ read.px(filename, encoding = NULL,
 This function reads data files in the PC-Axis format.
 The format is described in the two documents in the reference section.
 
-According to them, null values can be encoded using ".", "..", "...", or "....". 
+According to them, null values can be encoded using ".", "..", "...", "....", "....." or "......". 
 
 Also, the documentation is not very specific concerning the actual encoding to be expected in
 PC-Axis files.