diff --git a/vcf/parser.py b/vcf/parser.py
index c3c3d08..5b787c7 100644
--- a/vcf/parser.py
+++ b/vcf/parser.py
@@ -478,6 +478,8 @@ def _parse_samples(self, samples, samp_fmt, site):
                 # short circuit the most common
                 if samp_fmt._fields[i] == 'GT':
                     sampdat[i] = vals
+		    if vals == ".":
+		 	sampdat[i] = None
                     continue
                 # genotype filters are a special case
                 elif samp_fmt._fields[i] == 'FT':