diff --git a/HISTORY.md b/HISTORY.md
index cf03158b..27a9b98f 100755
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -9,6 +9,7 @@
 
 ### 2020-12-17
 * blocks: added hook for caching variadic inputs
+* blocks: refactored blockSequence() non-recursively
 
 ### 2020-12-16
 * threads, objects: added dev debugging hook for counting yields
diff --git a/src/blocks.js b/src/blocks.js
index ff6c315f..188e1ead 100644
--- a/src/blocks.js
+++ b/src/blocks.js
@@ -4818,12 +4818,13 @@ CommandBlockMorph.prototype.init = function () {
 // CommandBlockMorph enumerating:
 
 CommandBlockMorph.prototype.blockSequence = function () {
-    var nb = this.nextBlock(),
-        result = [this];
-    if (nb) {
-        result = result.concat(nb.blockSequence());
+    var sequence = [this],
+        nb = this.nextBlock();
+    while (nb) {
+        sequence.push(nb);
+        nb = nb.nextBlock();
     }
-    return result;
+    return sequence;
 };
 
 CommandBlockMorph.prototype.bottomBlock = function () {