diff --git a/spec/commands_spec.lua b/spec/commands_spec.lua
index c68c545..c105caa 100644
--- a/spec/commands_spec.lua
+++ b/spec/commands_spec.lua
@@ -51,7 +51,7 @@ describe("tests related to commands", function()
       assert.same({}, args)
 
       parser:require_command(true)
-      assert.has_error(function() parser:parse{} end, "command is required")
+      assert.has_error(function() parser:parse{} end, "a command is required")
    end)
 
    it("Detects wrong commands", function()
diff --git a/src/argparse.lua b/src/argparse.lua
index 673e29b..fc26c6d 100644
--- a/src/argparse.lua
+++ b/src/argparse.lua
@@ -746,7 +746,7 @@ function Parser:parse(args)
    end
 
    if parser._require_command and #commands > 0 then
-      parser:error("command is required")
+      parser:error("a command is required")
    end
 
    for _, option in ipairs(options) do