diff --git a/vis-lua.c b/vis-lua.c
index 909af5d5d..a3472b64c 100644
--- a/vis-lua.c
+++ b/vis-lua.c
@@ -3229,10 +3229,10 @@ void vis_lua_process_response(Vis *vis, const char *name,
 		case EXIT:
 		case SIGNAL:
 			lua_pushinteger(L, len);
-			lua_pushlstring(L, buffer, 0);
+			lua_pushnil(L);
 			break;
 		default:
-			lua_pushinteger(L, 0);
+			lua_pushnil(L);
 			lua_pushlstring(L, buffer, len);
 		}
 		pcall(vis, L, 4, 0);
diff --git a/vis-lua.h b/vis-lua.h
index 9b33cc07a..7ec865ae0 100644
--- a/vis-lua.h
+++ b/vis-lua.h
@@ -6,13 +6,13 @@
 #include <lualib.h>
 #include <lauxlib.h>
 
-#include "vis-subprocess.h"
 #else
 typedef struct lua_State lua_State;
 typedef void* lua_CFunction;
 #endif
 
 #include "vis.h"
+#include "vis-subprocess.h"
 /* add a directory to consider when loading lua files */
 bool vis_lua_path_add(Vis*, const char *path);
 /* get semicolon separated list of paths to load lua files
diff --git a/vis-subprocess.h b/vis-subprocess.h
index d64e79bac..2e4c22209 100644
--- a/vis-subprocess.h
+++ b/vis-subprocess.h
@@ -5,7 +5,11 @@
 #include <sys/select.h>
 
 typedef struct Process Process;
+#if CONFIG_LUA
 typedef int Invalidator(lua_State*);
+#else
+typedef void Invalidator;
+#endif
 
 struct Process {
 	char *name;