diff --git a/group.go b/group.go
index 27d2d72..6472420 100644
--- a/group.go
+++ b/group.go
@@ -278,7 +278,7 @@
 
 		if option.isBool() && option.Default != nil {
 			return newErrorf(ErrInvalidTag,
-				"boolean flag `%s' may not have default values, they always default to `false' and can only be turned off",
+				"boolean flag `%s' may not have default values, they always default to `false' and can only be turned on",
 				option.shortAndLongName())
 		}
 
diff --git a/parser_test.go b/parser_test.go
index a81983f..32afc69 100644
--- a/parser_test.go
+++ b/parser_test.go
@@ -139,9 +139,9 @@
 	}
 
 	if runtime.GOOS == "windows" {
-		assertParseFail(t, ErrInvalidTag, "boolean flag `/d' may not have default values, they always default to `false' and can only be turned off", &opts)
+		assertParseFail(t, ErrInvalidTag, "boolean flag `/d' may not have default values, they always default to `false' and can only be turned on", &opts)
 	} else {
-		assertParseFail(t, ErrInvalidTag, "boolean flag `-d' may not have default values, they always default to `false' and can only be turned off", &opts)
+		assertParseFail(t, ErrInvalidTag, "boolean flag `-d' may not have default values, they always default to `false' and can only be turned on", &opts)
 	}
 }