diff --git a/src/cligen/flag.cr b/src/cligen/flag.cr
index e6b8e71..c301de2 100644
--- a/src/cligen/flag.cr
+++ b/src/cligen/flag.cr
@@ -6,7 +6,7 @@ module CliGen
     type : String,
     array : Bool,
     format : String?,
-    default : String?,
+    default : String,
     options : Array(String)?
 
   abstract class BaseFlag
@@ -81,7 +81,7 @@ module CliGen
           default = @default.not_nil!.to_s
         {% end %}
       else
-        default = nil
+        default = ""
       end
       meta = FlagMeta.new(
         type: {{T.stringify}},
diff --git a/src/cligen/template/cmd_help.ecr b/src/cligen/template/cmd_help.ecr
index 344802f..33ddc28 100644
--- a/src/cligen/template/cmd_help.ecr
+++ b/src/cligen/template/cmd_help.ecr
@@ -14,7 +14,7 @@ Flags:
   <%- else -%>
     <%- flags = [flag.short,flag.long.strip] -%>
   <%- end -%>
-    <%= "%-#{len}s %s" % [flags.join(","), flag.description.strip] %><%= flag.meta.options.nil? ? "" : " (valid: #{flag.meta.options.not_nil!.join(", ")})" %><%= flag.meta.default.nil? ? "" : " (default: #{flag.meta.default.not_nil!})" %>
+    <%= "%-#{len}s %s" % [flags.join(","), flag.description.strip] %><%= flag.meta.options.nil? ? "" : " (valid: #{flag.meta.options.not_nil!.join(", ")})" %><%= flag.meta.default.empty? ? "" : " (default: #{flag.meta.default.not_nil!})" %>
   <%- if verbose? -%>
     <%= "%-#{len}s %s" % ["", "Type: #{flag.meta.type}"] %>
     <%= "%-#{len}s %s" % ["", "ENV VAR: #{flag.env_var}"] %>