diff --git a/.gitignore b/.gitignore
index 7e61b01..8f1ceee 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 **/.idea/
 **/.precomp/
-**/*.iml
\ No newline at end of file
+**/*.iml
+**/.DS_Store
\ No newline at end of file
diff --git a/Changes b/Changes
index 3dbad90..2259aa2 100644
--- a/Changes
+++ b/Changes
@@ -1,5 +1,8 @@
 Version history:
 
+1.6.2   2020-06-22  'fix concurrency issue'
+	- fix concurrency issue with laziness of the sequence operator
+
 1.6.1   2019-04-29  'conditional log calls'
 	- add methods info-on, error-on or so to check will a log will be written
 	- separate sprintf-slyte and contatenation-slyte logs into separate methods
diff --git a/META6.json b/META6.json
index 57ee25e..fac5343 100644
--- a/META6.json
+++ b/META6.json
@@ -1,7 +1,7 @@
 {
   "name": "LogP6",
   "description": "Full customisable logging library inspired by idea of separate logging and its configuration.",
-  "version": "1.6.1",
+  "version": "1.6.2",
   "perl": "6.d",
   "authors": [
     "Mikhail Khorkov"
diff --git a/lib/LogP6/WriterConf/Pattern.pm6 b/lib/LogP6/WriterConf/Pattern.pm6
index 6e209d6..156a50f 100644
--- a/lib/LogP6/WriterConf/Pattern.pm6
+++ b/lib/LogP6/WriterConf/Pattern.pm6
@@ -102,7 +102,9 @@ class XTrace does PatternPart {
 	method show($x) { $x.backtrace }
 }
 
-my $digits = ('00', '01' ... '99').List;
+# use explicit initialization (without sequence operator for example)
+# to avoid laziness which can lead to concurrency issues
+my $digits = <00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99>.List;
 my $months = <0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec>.List;
 
 class Date does PatternPart {