diff --git a/lib/biju/parser.rb b/lib/biju/parser.rb
index 4d46530..5cc6658 100644
--- a/lib/biju/parser.rb
+++ b/lib/biju/parser.rb
@@ -26,11 +26,11 @@ module Biju
 
     rule(:mgl) do
       (str('+CMGL').as(:cmd) >> str(': ') >> infos >> crlf >> message >> crlf)
-        .repeat.as(:sms) >> crlf
+        .repeat(1).as(:sms) >> crlf
     end
     rule(:num) do
       (str('+CNUM').as(:cmd) >> str(': ') >> array >> crlf)
-        .repeat.as(:phone_numbers) >> crlf >> crlf
+        .repeat(1).as(:phone_numbers) >> crlf >> crlf
     end
     rule(:mgf) do
       str('+CMGF').as(:cmd) >> str(': ') >> boolean.as(:result) >> crlf >> crlf
@@ -42,7 +42,7 @@ module Biju
       str('+CMGS').as(:cmd) >> str(': ') >> int.as(:result) >> crlf >> crlf
     end
     rule(:generic_response) do
-      match('[^:]').repeat.as(:cmd) >> str(': ') >> array >>
+      match('[^:]').repeat(1).as(:cmd) >> str(': ') >> array >>
       crlf >> crlf
     end
 
@@ -52,7 +52,7 @@ module Biju
     rule(:data) { (str('(') >> array >> str(')')) | info }
     rule(:infos) { (info >> (comma >> info).repeat).as(:infos) }
     rule(:info) { datetime | string | int | empty_string }
-    rule(:message) { match('[0-9A-Fa-f]').repeat.as(:message) }
+    rule(:message) { match('[0-9A-Fa-f]').repeat(1).as(:message) }
 
     # MISC
     rule(:status) { (ok | error).as(:status) }
@@ -84,20 +84,22 @@ module Biju
   class ATTransform < Parslet::Transform
     rule(prompt: simple(:prompt)) { { prompt: true } }
     rule(cmd: simple(:cmd), infos: subtree(:infos), message: simple(:message)) do
-      {cmd: cmd.to_s, infos: infos, message: message.to_s}
+      { cmd: cmd.to_s, infos: infos, message: message.to_s }
     end
     rule(cmd: simple(:cmd), array: subtree(:array)) do
-      {cmd: cmd.to_s, array: array}
+      { cmd: cmd.to_s, array: array }
     end
     rule(cmd: simple(:cmd), result: simple(:result)) do
-      {cmd: cmd.to_s, result: result}
+      { cmd: cmd.to_s, result: result }
     end
 
     rule(empty_string: simple(:empty_string)) { '' }
     rule(int: simple(:int)) { int.to_i }
     rule(boolean: simple(:boolean)) { boolean.to_i > 0 }
     rule(string: simple(:string)) { string.to_s }
-    rule(datetime: simple(:datetime)) { DateTime.strptime(datetime.to_s, "%y/%m/%d,%T%Z") }
+    rule(datetime: simple(:datetime)) do
+      DateTime.strptime(datetime.to_s, '%y/%m/%d,%T%Z')
+    end
     rule(array: subtree(:array)) { array }
 
     rule(status: simple(:status)) { { status: status } }
diff --git a/lib/biju/pdu.rb b/lib/biju/pdu.rb
index 15b40d4..d6a7ba3 100644
--- a/lib/biju/pdu.rb
+++ b/lib/biju/pdu.rb
@@ -24,13 +24,13 @@ module Biju
         '%02x' % first_octet.binary,
         # TP-Message-Reference
         '00',
-        "%02x" % phone_number.length,
-        "%02x" % phone_number.type_of_address.hex,
+        '%02x' % phone_number.length,
+        '%02x' % phone_number.type_of_address.hex,
         phone_number.number,
         # TP-PID: Protocol identifier
         '00',
-        "%02x" % user_data.encoding.hex,
-        "%02x" % user_data.length,
+        '%02x' % user_data.encoding.hex,
+        '%02x' % user_data.length,
         user_data.message
       ].join
     end
diff --git a/lib/biju/pdu/encoding/gsm7bit.rb b/lib/biju/pdu/encoding/gsm7bit.rb
index 758b063..242c612 100644
--- a/lib/biju/pdu/encoding/gsm7bit.rb
+++ b/lib/biju/pdu/encoding/gsm7bit.rb
@@ -38,7 +38,7 @@ module Biju
             # Only keep the bits for the current character and
             # add relevant bits from the previous octet
             # to get the full septet and decode the current character
-            current = ((octet & (2 ** (7 - index) - 1)) << index) | next_char
+            current = ((octet & (2**(7 - index) - 1)) << index) | next_char
 
             res = add_char(res, current)
             current_length += 1
diff --git a/lib/biju/pdu/encoding/ucs2.rb b/lib/biju/pdu/encoding/ucs2.rb
index f557965..a5360f6 100644
--- a/lib/biju/pdu/encoding/ucs2.rb
+++ b/lib/biju/pdu/encoding/ucs2.rb
@@ -9,7 +9,9 @@ module Biju
 
         def self.encode(string)
           [
-            string.encode('UCS-2BE').chars.map { |char| "%04x" % char.ord }.join,
+            string.encode('UCS-2BE').chars.map do |char|
+              '%04x' % char.ord
+            end.join,
             length: string.length * 2,
           ]
         end