diff --git a/glfw/src/Window.zig b/glfw/src/Window.zig
index f76184ef..4aa7a467 100644
--- a/glfw/src/Window.zig
+++ b/glfw/src/Window.zig
@@ -2194,39 +2194,38 @@ test "setTitle" {
     try window.setTitle("Updated title!");
 }
 
-// TODO(window): test appears to fail on at least Linux, image size is potentially wrong.
-// test "setIcon" {
-//     const allocator = testing.allocator;
-//     const glfw = @import("main.zig");
-//     try glfw.init();
-//     defer glfw.terminate();
+test "setIcon" {
+    const allocator = testing.allocator;
+    const glfw = @import("main.zig");
+    try glfw.init();
+    defer glfw.terminate();
 
-//     const window = glfw.Window.create(640, 480, "Hello, Zig!", null, null) catch |err| {
-//         // return without fail, because most of our CI environments are headless / we cannot open
-//         // windows on them.
-//         std.debug.print("note: failed to create window: {}\n", .{err});
-//         return;
-//     };
-//     defer window.destroy();
+    const window = glfw.Window.create(640, 480, "Hello, Zig!", null, null) catch |err| {
+        // return without fail, because most of our CI environments are headless / we cannot open
+        // windows on them.
+        std.debug.print("note: failed to create window: {}\n", .{err});
+        return;
+    };
+    defer window.destroy();
 
-//     // Create an all-red icon image.
-//     var width: usize = 48;
-//     var height: usize = 48;
-//     const icon = try Image.init(allocator, width, height, width * height * 4);
-//     var x: usize = 0;
-//     var y: usize = 0;
-//     while (y <= height) : (y += 1) {
-//         while (x <= width) : (x += 1) {
-//             icon.pixels[(x * y * 4) + 0] = 255; // red
-//             icon.pixels[(x * y * 4) + 1] = 0; // green
-//             icon.pixels[(x * y * 4) + 2] = 0; // blue
-//             icon.pixels[(x * y * 4) + 3] = 255; // alpha
-//         }
-//     }
-//     window.setIcon(allocator, &[_]Image{icon}) catch |err| std.debug.print("can't set window icon, wayland maybe? error={}\n", .{err});
+    // Create an all-red icon image.
+    var width: usize = 48;
+    var height: usize = 48;
+    const icon = try Image.init(allocator, width, height, width * height * 4);
+    var x: usize = 0;
+    var y: usize = 0;
+    while (y <= height) : (y += 1) {
+        while (x <= width) : (x += 1) {
+            icon.pixels[(x * y * 4) + 0] = 255; // red
+            icon.pixels[(x * y * 4) + 1] = 0; // green
+            icon.pixels[(x * y * 4) + 2] = 0; // blue
+            icon.pixels[(x * y * 4) + 3] = 255; // alpha
+        }
+    }
+    window.setIcon(allocator, &[_]Image{icon}) catch |err| std.debug.print("can't set window icon, wayland maybe? error={}\n", .{err});
 
-//     icon.deinit(allocator); // glfw copies it.
-// }
+    icon.deinit(allocator); // glfw copies it.
+}
 
 test "getPos" {
     const glfw = @import("main.zig");
diff --git a/glfw/upstream/glfw/src/x11_window.c b/glfw/upstream/glfw/src/x11_window.c
index d52ebc4d..27d51dc2 100644
--- a/glfw/upstream/glfw/src/x11_window.c
+++ b/glfw/upstream/glfw/src/x11_window.c
@@ -2133,10 +2133,10 @@ void _glfwPlatformSetWindowIcon(_GLFWwindow* window,
 
             for (j = 0;  j < images[i].width * images[i].height;  j++)
             {
-                *target++ = (images[i].pixels[j * 4 + 0] << 16) |
-                            (images[i].pixels[j * 4 + 1] <<  8) |
-                            (images[i].pixels[j * 4 + 2] <<  0) |
-                            (images[i].pixels[j * 4 + 3] << 24);
+                *target++ = (((long)images[i].pixels[j * 4 + 0]) << 16) |
+                            (((long)images[i].pixels[j * 4 + 1]) <<  8) |
+                            (((long)images[i].pixels[j * 4 + 2]) <<  0) |
+                            (((long)images[i].pixels[j * 4 + 3]) << 24);
             }
         }