diff --git a/lib/std/heap.zig b/lib/std/heap.zig
index 9ff8b9f7b9657099470a93513ca72100004a42d7..d456407706ffcf2dc5ec746f842ca92edd433984 100644
--- a/lib/std/heap.zig
+++ b/lib/std/heap.zig
@@ -325,7 +325,7 @@ const WasmPageAllocator = struct {
 
     var _conventional_data = [_]u128{0} ** 16;
     // Marking `conventional` as const saves ~40 bytes
-    var conventional = FreeBlock{ .data = &_conventional_data };
+    const conventional = FreeBlock{ .data = &_conventional_data };
     var extended = FreeBlock{ .data = &[_]u128{} };
 
     fn extendedOffset() usize {