diff --git a/src/arch/x86_64/CodeGen.zig b/src/arch/x86_64/CodeGen.zig
index 059f4b31f9..769e0401dc 100644
--- a/src/arch/x86_64/CodeGen.zig
+++ b/src/arch/x86_64/CodeGen.zig
@@ -1261,10 +1261,14 @@ fn airSlicePtr(self: *Self, inst: Air.Inst.Index) !void {
 
 fn airSliceLen(self: *Self, inst: Air.Inst.Index) !void {
     const ty_op = self.air.instructions.items(.data)[inst].ty_op;
-    const result: MCValue = if (self.liveness.isUnused(inst))
-        .dead
-    else
-        return self.fail("TODO implement slice_len for {}", .{self.target.cpu.arch});
+    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else result: {
+        const operand = try self.resolveInst(ty_op.operand);
+        const dst_mcv: MCValue = switch (operand) {
+            .stack_offset => |off| MCValue{ .stack_offset = off + 4 },
+            else => return self.fail("TODO implement slice_len for {}", .{operand}),
+        };
+        break :result dst_mcv;
+    };
     return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
 }