diff --git a/make.h b/make.h
index e46a150d..0b486a0f 100644
--- a/make.h
+++ b/make.h
@@ -502,6 +502,7 @@ extern int env_overrides, no_builtin_rules_flag, no_builtin_variables_flag;
 extern int print_version_flag, print_directory_flag, check_symlink_flag;
 extern int warn_undefined_variables_flag, posix_pedantic, not_parallel;
 extern int second_expansion, clock_skew_detected, rebuilding_makefiles;
+extern int one_shell;
 
 /* can we run commands via 'sh -c xxx' or must we use batch files? */
 extern int batch_mode_shell;