diff --git a/README.md b/README.md
index 8a13c83b..be7e69f1 100644
--- a/README.md
+++ b/README.md
@@ -112,10 +112,11 @@ Define alias for a subcommand
  ## @option    --foo!               A required option
  ## @option    --foo*               A option with multiple values
  ## @option    --foo+               A required option with multiple values
+ ## @option    --foo=a              A option with default
  ## @option    --foo[a|b]           A option with choices
  ## @option    --foo[=a|b]          A option with choices and default value
- ## @option -f --foo <PATH>         A option with short alias and notation
  ## @option    --foo![a|b]          A required option with choices
+ ## @option -f --foo <PATH>         A option with short alias and notation
 ```
 
 Define value option
@@ -160,6 +161,7 @@ Define flag option
 # @arg value!           A required positional argument
 # @arg value*           A positional argument support multiple values
 # @arg value+           A required positional argument support multiple values
+# @arg value=a          A positional argument with default value
 # @arg value[a|b]       A positional argument with choices
 # @arg value[=a|b]      A positional argument with choices and default value
 # @arg value![a|b]      A required positional argument with choices
@@ -168,11 +170,7 @@ Define positional argument
 
 #### modifier
 
-- `*`: occur multiple times, optional
-- `+`: occur multiple times, required
-- `!`: required
-- `[a|b|c]`: choices
-- `![a|b|c]`: choices, required
+See [option's modifier](#modifier)
 
 ## License
 
diff --git a/src/parser.rs b/src/parser.rs
index b27fe984..d8239fa8 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -314,6 +314,7 @@ fn parse_positional_arg(input: &str) -> nom::IResult<&str, ArgData> {
                 parse_arg_choices_default,
                 parse_arg_choices_required,
                 parse_arg_choices,
+                parse_arg_assign,
                 parse_arg_mark,
             )),
             parse_tail,
@@ -627,6 +628,7 @@ mod tests {
         assert_parse_positional_arg!("foo!");
         assert_parse_positional_arg!("foo+");
         assert_parse_positional_arg!("foo*");
+        assert_parse_positional_arg!("foo=a");
         assert_parse_positional_arg!("foo[a|b]");
         assert_parse_positional_arg!("foo[=a|b]");
         assert_parse_positional_arg!("foo![a|b]");
diff --git a/tests/snapshots/integration__spec_test__spec_cmd_positional_with_default.snap b/tests/snapshots/integration__spec_test__spec_cmd_positional_with_default.snap
new file mode 100644
index 00000000..7ddc6735
--- /dev/null
+++ b/tests/snapshots/integration__spec_test__spec_cmd_positional_with_default.snap
@@ -0,0 +1,26 @@
+---
+source: tests/spec_test.rs
+assertion_line: 115
+expression: output
+
+---
+RUN
+spec cmd-positional-with-default -h
+
+STDOUT
+
+
+STDERR
+spec-cmd-positional-with-default 
+Positional with default value
+
+USAGE:
+    spec cmd-positional-with-default [ARG]
+
+ARGS:
+    <ARG>    A arg with default value [default: a]
+
+OPTIONS:
+    -h, --help    Print help information
+
+
diff --git a/tests/snapshots/integration__spec_test__spec_cmd_positional_with_default_exec.snap b/tests/snapshots/integration__spec_test__spec_cmd_positional_with_default_exec.snap
new file mode 100644
index 00000000..a2e1386e
--- /dev/null
+++ b/tests/snapshots/integration__spec_test__spec_cmd_positional_with_default_exec.snap
@@ -0,0 +1,16 @@
+---
+source: tests/spec_test.rs
+assertion_line: 123
+expression: output
+
+---
+RUN
+spec cmd-positional-with-default
+
+STDOUT
+argc_arg=a
+argc__call=cmd_positional_with_default
+
+STDERR
+
+
diff --git a/tests/snapshots/integration__spec_test__spec_help.snap b/tests/snapshots/integration__spec_test__spec_help.snap
index 65991ef8..5c696f3e 100644
--- a/tests/snapshots/integration__spec_test__spec_help.snap
+++ b/tests/snapshots/integration__spec_test__spec_help.snap
@@ -45,6 +45,8 @@ SUBCOMMANDS:
             Positional with choices and value
     cmd-positional-with-choices-and-required
             Positional with choices and required
+    cmd-positional-with-default
+            Positional with default value
     cmd-preferred
             Preferred
     cmd-without-any-arg
diff --git a/tests/spec.sh b/tests/spec.sh
index bf197e53..455e79c9 100644
--- a/tests/spec.sh
+++ b/tests/spec.sh
@@ -62,14 +62,14 @@ cmd_flag_formats() {
 }
 
 # @cmd  Positional one required
-# @arg   arg1!   A required arg
+# @arg   arg1!     A required arg
 cmd_positional_only() {
     print_argc_vars
 }
 
 # @cmd  Positional all required
-# @arg   arg1!  A required arg
-# @arg   arg2+  A required arg, multiple
+# @arg   arg1!     A required arg
+# @arg   arg2+     A required arg, multiple
 cmd_positional_requires() {
     print_argc_vars
 }
@@ -80,6 +80,12 @@ cmd_positional_with_choices() {
     print_argc_vars
 }
 
+# @cmd  Positional with default value
+# @arg   arg=a      A arg with default value
+cmd_positional_with_default() {
+    print_argc_vars
+}
+
 # @cmd  Positional with choices and value
 # @arg   arg[=a|b]   A arg with choices and default value
 cmd_positional_with_choices_and_default() {
diff --git a/tests/spec_test.rs b/tests/spec_test.rs
index accac3f7..f664103f 100644
--- a/tests/spec_test.rs
+++ b/tests/spec_test.rs
@@ -110,6 +110,22 @@ fn test_spec_cmd_option_names_exec_eval() {
     );
 }
 
+#[test]
+fn test_spec_cmd_positional_with_default() {
+    snapshot!(
+        include_str!("spec.sh"),
+        &["spec", "cmd-positional-with-default", "-h"],
+    );
+}
+
+#[test]
+fn test_spec_cmd_positional_with_default_exec() {
+    snapshot!(
+        include_str!("spec.sh"),
+        &["spec", "cmd-positional-with-default"],
+    );
+}
+
 #[test]
 fn test_spec_cmd_positional_with_choices() {
     snapshot!(