diff --git a/.changeset/angry-trainers-remember.md b/.changeset/angry-trainers-remember.md
new file mode 100644
index 00000000..8ca3ac73
--- /dev/null
+++ b/.changeset/angry-trainers-remember.md
@@ -0,0 +1,5 @@
+---
+"@tsplus/stdlib": patch
+---
+
+Fix HashMap Modify
diff --git a/packages/stdlib/_src/collections/HashMap/_internal/node.ts b/packages/stdlib/_src/collections/HashMap/_internal/node.ts
index 64b4d285..ba4be95f 100644
--- a/packages/stdlib/_src/collections/HashMap/_internal/node.ts
+++ b/packages/stdlib/_src/collections/HashMap/_internal/node.ts
@@ -214,15 +214,23 @@ export class IndexedNode<K, V> {
     const bit = toBitmap(frag)
     const indx = fromBitmap(mask, bit)
     const exists = mask & bit
-    const current = exists ? children[indx]! : new EmptyNode<K, V>()
+    const canEdit = canEditNode(this, edit)
+
+    if (!exists) {
+      const _newChild = new EmptyNode<K, V>().modify(edit, shift + SIZE, f, hash, key, size)
+      if (!_newChild) return this
+      return children.length >= MAX_INDEX_NODE ?
+        expand(edit, frag, _newChild, mask, children) :
+        new IndexedNode(edit, mask | bit, arraySpliceIn(canEdit, indx, _newChild, children))
+    }
+
+    const current = children[indx]!
     const child = current.modify(edit, shift + SIZE, f, hash, key, size)
 
     if (current === child) return this
-
-    const canEdit = canEditNode(this, edit)
     let bitmap = mask
     let newChildren
-    if (exists && isEmptyNode(child)) {
+    if (isEmptyNode(child)) {
       // remove
       bitmap &= ~bit
       if (!bitmap) return new EmptyNode()
@@ -231,14 +239,6 @@ export class IndexedNode<K, V> {
       }
 
       newChildren = arraySpliceOut(canEdit, indx, children)
-    } else if (!exists && !isEmptyNode(child)) {
-      // add
-      if (children.length >= MAX_INDEX_NODE) {
-        return expand(edit, frag, child, mask, children)
-      }
-
-      bitmap |= bit
-      newChildren = arraySpliceIn(canEdit, indx, child, children)
     } else {
       // modify
       newChildren = arrayUpdate(canEdit, indx, child, children)
@@ -249,6 +249,7 @@ export class IndexedNode<K, V> {
       this.children = newChildren
       return this
     }
+
     return new IndexedNode(edit, bitmap, newChildren)
   }
 }
diff --git a/packages/stdlib/_test/Differ.test.ts b/packages/stdlib/_test/Differ.test.ts
index d3a3829e..fe8e99b4 100644
--- a/packages/stdlib/_test/Differ.test.ts
+++ b/packages/stdlib/_test/Differ.test.ts
@@ -1,8 +1,16 @@
+import { it as it_ } from "vitest"
+
 function diffLaws<Value, Patch>(
   differ: Differ<Value, Patch>,
   gen: () => Value,
   equal: (a: Value, b: Value) => boolean
 ): void {
+  const it = (name: string, f: () => void) =>
+    it_(name, () => {
+      for (let i = 0; i < 100; i++) {
+        f()
+      }
+    })
   describe.concurrent("differ laws", () => {
     it("combining patches is associative", () => {
       const value1 = gen()
@@ -57,9 +65,9 @@ function randomChunk(): Chunk<number> {
   return Chunk.fill(20, smallInt)
 }
 
-// function randomHashMap(): HashMap<number, number> {
-//   return HashMap.from(Chunk.fill(20, smallInt).zip(Chunk.fill(20, smallInt)))
-// }
+function randomHashMap(): HashMap<number, number> {
+  return HashMap.from(Chunk.fill(2, smallInt).zip(Chunk.fill(2, smallInt)))
+}
 
 function randomHashSet(): HashSet<number> {
   return HashSet.from(Chunk.fill(20, smallInt))
@@ -93,7 +101,7 @@ describe.concurrent("Differ", () => {
   describe.concurrent("hashMap", () => {
     diffLaws(
       Differ.hashMap<number, number, (n: number) => number>(Differ.update<number>()),
-      () => HashMap(Tuple(1, 2), Tuple(3, 4), Tuple(5, 6)),
+      randomHashMap,
       Equals.equals
     )
   })
diff --git a/packages/stdlib/_test/HashMap.test.ts b/packages/stdlib/_test/HashMap.test.ts
index 3715fd98..e99b9fc0 100644
--- a/packages/stdlib/_test/HashMap.test.ts
+++ b/packages/stdlib/_test/HashMap.test.ts
@@ -287,6 +287,11 @@ describe.concurrent("HashMap", () => {
     assert.isTrue(result[key(1)] == Maybe.some(value("b")))
   })
 
+  it("remove non existing key doesn't change the array", () => {
+    const map = HashMap(Tuple(13, 95), Tuple(90, 4))
+    assert.deepEqual(map.remove(75).keySet.toArray, map.keySet.toArray)
+  })
+
   it("removeMany", () => {
     const hashMap = HashMap(Tuple(key(0), value("a")), Tuple(key(1), value("b")))