diff --git a/src/arch/x86_64/CodeGen.zig b/src/arch/x86_64/CodeGen.zig
index 6063c38074ca306a2970f9ced1d762255edd9311..2e0c5f64f8c806850341265b604715d10dacb0f2 100644
--- a/src/arch/x86_64/CodeGen.zig
+++ b/src/arch/x86_64/CodeGen.zig
@@ -11162,6 +11162,12 @@ fn airAggregateInit(self: *Self, inst: Air.Inst.Index) !void {
                     const elem_off = @intCast(i32, elem_size * elem_i);
                     try self.genSetMem(.{ .frame = frame_index }, elem_off, elem_ty, mat_elem_mcv);
                 }
+                if (result_ty.sentinel()) |sentinel| try self.genSetMem(
+                    .{ .frame = frame_index },
+                    @intCast(i32, elem_size * elements.len),
+                    elem_ty,
+                    try self.genTypedValue(.{ .ty = elem_ty, .val = sentinel }),
+                );
                 break :result .{ .load_frame = .{ .index = frame_index } };
             },
             .Vector => return self.fail("TODO implement aggregate_init for vectors", .{}),
diff --git a/test/behavior/eval.zig b/test/behavior/eval.zig
index f4c75149a89cb78f84fa5aee677b8fc6cc29c08a..d22eba4fa0ebc4b374c7a06c0d887380ee28ffd8 100644
--- a/test/behavior/eval.zig
+++ b/test/behavior/eval.zig
@@ -816,7 +816,6 @@ test "array concatenation peer resolves element types - pointer" {
 
 test "array concatenation sets the sentinel - value" {
     if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
@@ -855,7 +854,6 @@ test "array concatenation sets the sentinel - pointer" {
 
 test "array multiplication sets the sentinel - value" {
     if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO