diff --git a/changelog.md b/changelog.md
index 0a397058..8f3fc4a3 100644
--- a/changelog.md
+++ b/changelog.md
@@ -2,6 +2,10 @@ Lite XL is following closely [rxi/lite](https://github.com/rxi/lite) but with so
 
 This files document the changes done in Lite XL for each release.
 
+### next release
+
+Add `system.set_window_opacity` function.
+
 ### 1.16.5
 
 Hotfix for Github's issue https://github.com/franko/lite-xl/issues/122
diff --git a/src/api/system.c b/src/api/system.c
index 56880616..bd8521ef 100644
--- a/src/api/system.c
+++ b/src/api/system.c
@@ -454,6 +454,13 @@ static int f_fuzzy_match(lua_State *L) {
   return 1;
 }
 
+static int f_set_window_opacity(lua_State *L) {
+  double n = luaL_checknumber(L, 1);
+  int r = SDL_SetWindowOpacity(window, n);
+  lua_pushboolean(L, r > -1);
+  return 1;
+}
+
 
 static const luaL_Reg lib[] = {
   { "poll_event",          f_poll_event          },
@@ -477,6 +484,7 @@ static const luaL_Reg lib[] = {
   { "sleep",               f_sleep               },
   { "exec",                f_exec                },
   { "fuzzy_match",         f_fuzzy_match         },
+  { "set_window_opacity",  f_set_window_opacity  },
   { NULL, NULL }
 };