diff --git a/build/lib/liqa_src/PreProcess_gtf.pl b/build/lib/liqa_src/PreProcess_gtf.pl
index 6b26b80..ec46586 100644
--- a/build/lib/liqa_src/PreProcess_gtf.pl
+++ b/build/lib/liqa_src/PreProcess_gtf.pl
@@ -62,8 +62,8 @@
         my @sss = split(";", $exonstarts{$gene}{$trans});
         my @eee = split(";", $exonends{$gene}{$trans});
 
-        my @sss_sort = sort @sss;
-        my @eee_sort = sort @eee;
+        my @sss_sort = sort {$a <=> $b} @sss;
+        my @eee_sort = sort {$a <=> $b} @eee;
 
         my $starts;
         my $ends;
diff --git a/build/scripts-3.7/PreProcess_gtf.pl b/build/scripts-3.7/PreProcess_gtf.pl
index 6b26b80..ec46586 100755
--- a/build/scripts-3.7/PreProcess_gtf.pl
+++ b/build/scripts-3.7/PreProcess_gtf.pl
@@ -62,8 +62,8 @@
         my @sss = split(";", $exonstarts{$gene}{$trans});
         my @eee = split(";", $exonends{$gene}{$trans});
 
-        my @sss_sort = sort @sss;
-        my @eee_sort = sort @eee;
+        my @sss_sort = sort {$a <=> $b} @sss;
+        my @eee_sort = sort {$a <=> $b} @eee;
 
         my $starts;
         my $ends;
diff --git a/dist/liqa-1.1.20.tar.gz b/dist/liqa-1.1.20.tar.gz
deleted file mode 100644
index f152cba..0000000
Binary files a/dist/liqa-1.1.20.tar.gz and /dev/null differ
diff --git a/dist/liqa-1.1.20-py3-none-any.whl b/dist/liqa-1.1.21-py3-none-any.whl
similarity index 77%
rename from dist/liqa-1.1.20-py3-none-any.whl
rename to dist/liqa-1.1.21-py3-none-any.whl
index dd988f0..8e85821 100644
Binary files a/dist/liqa-1.1.20-py3-none-any.whl and b/dist/liqa-1.1.21-py3-none-any.whl differ
diff --git a/dist/liqa-1.1.21.tar.gz b/dist/liqa-1.1.21.tar.gz
new file mode 100644
index 0000000..a642feb
Binary files /dev/null and b/dist/liqa-1.1.21.tar.gz differ
diff --git a/liqa.egg-info/PKG-INFO b/liqa.egg-info/PKG-INFO
index 7caa950..790ff3f 100644
--- a/liqa.egg-info/PKG-INFO
+++ b/liqa.egg-info/PKG-INFO
@@ -1,6 +1,6 @@
 Metadata-Version: 2.1
 Name: liqa
-Version: 1.1.20
+Version: 1.1.21
 Summary: A statistical tool to quantify isoform-specific expression using long-read RNA-seq
 Home-page: https://github.com/WGLab/LIQA
 Author: Yu Hu
diff --git a/setup.py b/setup.py
index 92e2df1..8487865 100644
--- a/setup.py
+++ b/setup.py
@@ -5,7 +5,7 @@
 
 setuptools.setup(
     name="liqa",
-    version="1.1.20",
+    version="1.1.21",
     author="Yu Hu",
     author_email="huyu999999@gmail.com",
     description="A statistical tool to quantify isoform-specific expression using long-read RNA-seq",