diff --git a/compiler/forget/src/HIR/BuildHIR.ts b/compiler/forget/src/HIR/BuildHIR.ts
index c994aae9e5..bb7a563990 100644
--- a/compiler/forget/src/HIR/BuildHIR.ts
+++ b/compiler/forget/src/HIR/BuildHIR.ts
@@ -340,6 +340,7 @@ function lowerStatement(
 
       const updateBlock = builder.enter((blockId) => {
         const update = stmt.get("update");
+        todoInvariant(update.hasNode(), "Handle empty for updater");
         if (update.hasNode()) {
           lowerExpressionToVoid(builder, update);
         }
@@ -1275,20 +1276,21 @@ function lowerExpressionToPlace(
   return place;
 }
 
+/**
+ * Lowers an expression to an instruction with no lvalue
+ */
 function lowerExpressionToVoid(
   builder: HIRBuilder,
   exprPath: NodePath<t.Expression>
 ): void {
   const instr = lowerExpression(builder, exprPath);
-  if (instr.kind !== "Identifier") {
-    const exprLoc = exprPath.node.loc ?? GeneratedSource;
-    builder.push({
-      id: makeInstructionId(0),
-      value: instr,
-      loc: exprLoc,
-      lvalue: null,
-    });
-  }
+  const exprLoc = exprPath.node.loc ?? GeneratedSource;
+  builder.push({
+    id: makeInstructionId(0),
+    value: instr,
+    loc: exprLoc,
+    lvalue: null,
+  });
 }
 
 function lowerLVal(builder: HIRBuilder, exprPath: NodePath<t.LVal>): Place {
diff --git a/compiler/forget/src/HIR/Codegen.ts b/compiler/forget/src/HIR/Codegen.ts
index e8aa9dbf97..33f444c90d 100644
--- a/compiler/forget/src/HIR/Codegen.ts
+++ b/compiler/forget/src/HIR/Codegen.ts
@@ -137,9 +137,13 @@ class CodegenVisitor
   appendValueBlock(block: t.Statement[], item: t.Statement): void {
     this.appendBlock(block, item);
   }
-  leaveValueBlock(block: t.Statement[], place: t.Expression): t.Expression {
+  leaveValueBlock(
+    block: t.Statement[],
+    place: t.Expression | null
+  ): t.Expression {
     this.depth--;
     if (block.length === 0) {
+      invariant(place !== null, "Unexpected empty value block");
       return place;
     }
     const expressions = block.map((stmt) => {
@@ -153,7 +157,9 @@ class CodegenVisitor
           );
       }
     });
-    expressions.push(place);
+    if (place !== null) {
+      expressions.push(place);
+    }
     return t.sequenceExpression(expressions);
   }
 
diff --git a/compiler/forget/src/HIR/HIRTreeVisitor.ts b/compiler/forget/src/HIR/HIRTreeVisitor.ts
index 7979e8646a..30cae5e64f 100644
--- a/compiler/forget/src/HIR/HIRTreeVisitor.ts
+++ b/compiler/forget/src/HIR/HIRTreeVisitor.ts
@@ -451,24 +451,27 @@ class Driver<TBlock, TInit, TValueBlock, TValue, TStatement, TCase> {
   ): TValue {
     const valueBlock = this.visitor.enterValueBlock(parent);
     const instructions = [...block.instructions];
-    let lastValue: { value: InstructionValue; id: InstructionId };
+    let lastValue: { value: InstructionValue; id: InstructionId } | null = null;
     if (terminalValue != null) {
       lastValue = terminalValue;
     } else {
-      invariant(instructions.length > 0, "Value block may not be empty");
-      const last = instructions.pop()!;
-      invariant(
-        last.lvalue === null,
-        "Expected value block to end in a value, not an assignment"
-      );
-      lastValue = { value: last.value, id: last.id };
+      if (
+        instructions.length &&
+        instructions[instructions.length - 1].lvalue === null
+      ) {
+        const last = instructions.pop()!;
+        lastValue = { value: last.value, id: last.id };
+      }
     }
     for (const instr of instructions) {
       const value = this.visitor.visitValue(instr.value, instr.id);
       const item = this.visitor.visitInstruction(instr, value);
       this.visitor.appendValueBlock(valueBlock, item);
     }
-    const value = this.visitor.visitValue(lastValue.value, lastValue.id);
+    const value =
+      lastValue !== null
+        ? this.visitor.visitValue(lastValue.value, lastValue.id)
+        : null;
     return this.visitor.leaveValueBlock(valueBlock, value);
   }
 
@@ -817,7 +820,7 @@ export interface Visitor<
    * Converts the visitor's value block (and final value) to the visitor's
    * value representation.
    */
-  leaveValueBlock(block: TValueBlock, value: TValue): TValue;
+  leaveValueBlock(block: TValueBlock, value: TValue | null): TValue;
 
   enterInitBlock(block: TBlock): TValueBlock;
 
diff --git a/compiler/forget/src/HIR/InferReactiveScopes.ts b/compiler/forget/src/HIR/InferReactiveScopes.ts
index 0f767f9553..3f61f6ddeb 100644
--- a/compiler/forget/src/HIR/InferReactiveScopes.ts
+++ b/compiler/forget/src/HIR/InferReactiveScopes.ts
@@ -336,7 +336,10 @@ class AlignReactiveScopesToBlockScopeRangeVisitor
 {
   // For each block scope (outer array) stores a list of ReactiveScopes that start
   // in that block scope.
-  blockScopes: Array<Array<PendingReactiveScope>> = [];
+  blockScopes: Array<{
+    kind: "block" | "value";
+    scopes: Array<PendingReactiveScope>;
+  }> = [];
 
   // ReactiveScopes whose declaring block scope has ended but may still need to
   // be "closed" (ie have their range.end be updated). A given scope can be in
@@ -349,7 +352,10 @@ class AlignReactiveScopesToBlockScopeRangeVisitor
 
   visitId(id: InstructionId) {
     const currentScopes = this.blockScopes[this.blockScopes.length - 1]!;
-    const scopes = [...currentScopes, ...this.unclosedScopes];
+    if (currentScopes.kind === "value") {
+      return;
+    }
+    const scopes = [...currentScopes.scopes, ...this.unclosedScopes];
     for (const pending of scopes) {
       if (!pending.active) {
         continue;
@@ -362,7 +368,7 @@ class AlignReactiveScopesToBlockScopeRangeVisitor
   }
 
   enterBlock(): void {
-    this.blockScopes.push([]);
+    this.blockScopes.push({ kind: "block", scopes: [] });
   }
 
   appendBlock(block: void, item: void, label?: BlockId | undefined): void {}
@@ -370,10 +376,10 @@ class AlignReactiveScopesToBlockScopeRangeVisitor
   leaveBlock(block: void): void {
     const lastScope = this.blockScopes.pop();
     invariant(
-      lastScope !== undefined,
+      lastScope !== undefined && lastScope.kind === "block",
       "Expected enterBlock/leaveBlock to be called 1:1"
     );
-    for (const scope of lastScope) {
+    for (const scope of lastScope.scopes) {
       if (scope.active) {
         this.unclosedScopes.push(scope);
       }
@@ -381,19 +387,30 @@ class AlignReactiveScopesToBlockScopeRangeVisitor
   }
 
   enterValueBlock(): void {
-    this.enterBlock();
+    this.blockScopes.push({ kind: "value", scopes: [] });
   }
   appendValueBlock(block: void, item: void): void {}
   leaveValueBlock(block: void, value: void): void {
-    this.leaveBlock(block);
+    const lastScope = this.blockScopes.pop();
+    invariant(
+      lastScope !== undefined && lastScope.kind === "value",
+      "Expected enterValueBlock/leaveValueBlock to be called 1:1"
+    );
+    for (const scope of lastScope.scopes) {
+      invariant(
+        scope.active,
+        "Value scopes cannot be closed separately from the parent block"
+      );
+      this.unclosedScopes.push(scope);
+    }
   }
 
   enterInitBlock(block: void): void {
-    this.enterBlock();
+    this.enterValueBlock();
   }
   appendInitBlock(block: void, item: void): void {}
   leaveInitBlock(block: void): void {
-    this.leaveBlock(block);
+    this.leaveValueBlock(block);
   }
 
   visitInstruction(instruction: Instruction, value: void): void {
@@ -403,7 +420,7 @@ class AlignReactiveScopesToBlockScopeRangeVisitor
       if (!this.seenScopes.has(scope.id)) {
         const currentScopes = this.blockScopes[this.blockScopes.length - 1]!;
         this.seenScopes.add(scope.id);
-        currentScopes.push({
+        currentScopes.scopes.push({
           active: true,
           scope,
         });
diff --git a/compiler/forget/src/HIR/LeaveSSA.ts b/compiler/forget/src/HIR/LeaveSSA.ts
index 0f8fb49870..09787b9781 100644
--- a/compiler/forget/src/HIR/LeaveSSA.ts
+++ b/compiler/forget/src/HIR/LeaveSSA.ts
@@ -62,8 +62,17 @@ export function leaveSSA(fn: HIRFunction) {
       phis.push(...loop.phis);
     }
     if (terminal.kind === "for") {
+      const init = fn.body.blocks.get(terminal.init)!;
+      phis.push(...init.phis);
       const update = fn.body.blocks.get(terminal.update)!;
       phis.push(...update.phis);
+
+      // find declarations in the for init
+      for (const instr of init.instructions) {
+        if (instr.lvalue !== null && instr.lvalue.place.memberPath === null) {
+          hasDeclaration.add(instr.lvalue.place.identifier);
+        }
+      }
     }
 
     // For each phi, determine a canonical identifier to use for versions of the variable
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-for-trivial-update.expect.md b/compiler/forget/src/__tests__/fixtures/hir/ssa-for-trivial-update.expect.md
new file mode 100644
index 0000000000..446ebf66ad
--- /dev/null
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-for-trivial-update.expect.md
@@ -0,0 +1,113 @@
+
+## Input
+
+```javascript
+function foo() {
+  let x = 1;
+  for (let i = 0; i < 10; /* update is intentally a single identifier */ i) {
+    x += 1;
+  }
+  return x;
+}
+
+```
+
+## HIR
+
+```
+bb0:
+  [1] Let mutate x$6_@1[1:13] = 1
+  [2] For init=bb3 test=bb1 loop=bb5 update=bb4 fallthrough=bb2
+bb3:
+  predecessor blocks: bb0
+  [3] Const mutate i$7_@1[1:13] = 0
+  [4] Goto bb1
+bb1:
+  predecessor blocks: bb3 bb4
+  [5] Const mutate $8_@1[1:13] = 10
+  [6] Const mutate $10_@3[6:8] = Binary read i$7_@1 < read $8_@1
+  [7] If (read $10_@3) then:bb5 else:bb2 fallthrough=bb2
+bb5:
+  predecessor blocks: bb1
+  [8] Const mutate $11_@4 = 1
+  [9] Reassign mutate x$6_@1[1:13] = Binary read x$6_@1 + read $11_@4
+  [10] Goto(Continue) bb4
+bb4:
+  predecessor blocks: bb5
+  [11] read i$7_@1
+  [12] Goto bb1
+bb2:
+  predecessor blocks: bb1
+  [13] Return read x$6_@1
+
+```
+
+### CFG
+
+```mermaid
+flowchart TB
+  %% Basic Blocks
+  subgraph bb0
+    bb0_instrs["
+      [1] Let mutate x$6_@1[1:13] = 1
+    "]
+    bb0_instrs --> bb0_terminal(["For"])
+  end
+  subgraph bb3
+    bb3_instrs["
+      [3] Const mutate i$7_@1[1:13] = 0
+    "]
+    bb3_instrs --> bb3_terminal(["Goto"])
+  end
+  subgraph bb1
+    bb1_instrs["
+      [5] Const mutate $8_@1[1:13] = 10
+      [6] Const mutate $10_@3[6:8] = Binary read i$7_@1 < read $8_@1
+    "]
+    bb1_instrs --> bb1_terminal(["If (read $10_@3)"])
+  end
+  subgraph bb5
+    bb5_instrs["
+      [8] Const mutate $11_@4 = 1
+      [9] Reassign mutate x$6_@1[1:13] = Binary read x$6_@1 + read $11_@4
+    "]
+    bb5_instrs --> bb5_terminal(["Goto"])
+  end
+  subgraph bb4
+    bb4_instrs["
+      [11] read i$7_@1
+    "]
+    bb4_instrs --> bb4_terminal(["Goto"])
+  end
+  subgraph bb2
+    bb2_terminal(["Return read x$6_@1"])
+  end
+
+  %% Jumps
+  bb0_terminal -- "init" --> bb3
+  bb0_terminal -- "test" --> bb1
+  bb0_terminal -- "update" --> bb4
+  bb0_terminal -- "loop" --> bb5
+  bb0_terminal -- "fallthrough" --> bb2
+  bb3_terminal --> bb1
+  bb1_terminal -- "then" --> bb5
+  bb1_terminal -- "else" --> bb2
+  bb5_terminal --> bb4
+  bb4_terminal --> bb1
+
+```
+
+## Code
+
+```javascript
+function foo$0() {
+  let x$6 = 1;
+  bb2: for (const i$7 = 0; i$7 < 10; i$7) {
+    x$6 = x$6 + 1;
+  }
+
+  return x$6;
+}
+
+```
+      
\ No newline at end of file
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-for-trivial-update.js b/compiler/forget/src/__tests__/fixtures/hir/ssa-for-trivial-update.js
new file mode 100644
index 0000000000..ec6ed5cc75
--- /dev/null
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-for-trivial-update.js
@@ -0,0 +1,7 @@
+function foo() {
+  let x = 1;
+  for (let i = 0; i < 10; /* update is intentally a single identifier */ i) {
+    x += 1;
+  }
+  return x;
+}
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-for.expect.md b/compiler/forget/src/__tests__/fixtures/hir/ssa-for.expect.md
index 8543ea1bf1..2cbce2ee3b 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/ssa-for.expect.md
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-for.expect.md
@@ -4,7 +4,7 @@
 ```javascript
 function foo() {
   let x = 1;
-  for (let i = 0; i < 10; update()) {
+  for (let i = 0; i < 10; i += 1) {
     x += 1;
   }
   return x;
@@ -16,32 +16,32 @@ function foo() {
 
 ```
 bb0:
-  [1] Let mutate x$7_@0[1:13] = 1
+  [1] Let mutate x$7_@1[1:15] = 1
   [2] For init=bb3 test=bb1 loop=bb5 update=bb4 fallthrough=bb2
 bb3:
   predecessor blocks: bb0
-  [3] Const mutate i$8_@1[3:5] = 0
+  [3] Let mutate i$8_@1[1:15] = 0
   [4] Goto bb1
 bb1:
   predecessor blocks: bb3 bb4
-  [5] Const mutate $9_@2 = 10
-  [6] Const mutate $11_@3[6:8] = Binary read i$8_@1 < read $9_@2
-  [7] If (read $11_@3) then:bb5 else:bb2 fallthrough=bb2
+  [5] Const mutate $9_@1[1:15] = 10
+  [6] Const mutate $11_@1[1:15] = Binary read i$8_@1 < read $9_@1
+  [7] If (read $11_@1) then:bb5 else:bb2 fallthrough=bb2
 bb5:
   predecessor blocks: bb1
-  [8] Const mutate $12_@4 = 1
-  [9] Reassign mutate x$7_@0[1:13] = Binary read x$7_@0 + read $12_@4
+  [8] Const mutate $12_@3 = 1
+  [9] Reassign mutate x$7_@1[1:15] = Binary read x$7_@1 + read $12_@3
   [10] Goto(Continue) bb4
 bb4:
   predecessor blocks: bb5
-  [11] Call mutate update$3_@5()
-  [12] Goto bb1
+  [11] Const mutate $15_@1[1:15] = 1
+  [12] Reassign mutate i$8_@1[1:15] = Binary read i$8_@1 + read $15_@1
+  [13] read i$8_@1
+  [14] Goto bb1
 bb2:
   predecessor blocks: bb1
-  [13] Return read x$7_@0
-scope3 [6:8]:
-  - dependency: read i$8_@1
-  - dependency: read $9_@2
+  [15] Return read x$7_@1
+
 ```
 
 ### CFG
@@ -51,38 +51,40 @@ flowchart TB
   %% Basic Blocks
   subgraph bb0
     bb0_instrs["
-      [1] Let mutate x$7_@0[1:13] = 1
+      [1] Let mutate x$7_@1[1:15] = 1
     "]
     bb0_instrs --> bb0_terminal(["For"])
   end
   subgraph bb3
     bb3_instrs["
-      [3] Const mutate i$8_@1[3:5] = 0
+      [3] Let mutate i$8_@1[1:15] = 0
     "]
     bb3_instrs --> bb3_terminal(["Goto"])
   end
   subgraph bb1
     bb1_instrs["
-      [5] Const mutate $9_@2 = 10
-      [6] Const mutate $11_@3[6:8] = Binary read i$8_@1 < read $9_@2
+      [5] Const mutate $9_@1[1:15] = 10
+      [6] Const mutate $11_@1[1:15] = Binary read i$8_@1 < read $9_@1
     "]
-    bb1_instrs --> bb1_terminal(["If (read $11_@3)"])
+    bb1_instrs --> bb1_terminal(["If (read $11_@1)"])
   end
   subgraph bb5
     bb5_instrs["
-      [8] Const mutate $12_@4 = 1
-      [9] Reassign mutate x$7_@0[1:13] = Binary read x$7_@0 + read $12_@4
+      [8] Const mutate $12_@3 = 1
+      [9] Reassign mutate x$7_@1[1:15] = Binary read x$7_@1 + read $12_@3
     "]
     bb5_instrs --> bb5_terminal(["Goto"])
   end
   subgraph bb4
     bb4_instrs["
-      [11] Call mutate update$3_@5()
+      [11] Const mutate $15_@1[1:15] = 1
+      [12] Reassign mutate i$8_@1[1:15] = Binary read i$8_@1 + read $15_@1
+      [13] read i$8_@1
     "]
     bb4_instrs --> bb4_terminal(["Goto"])
   end
   subgraph bb2
-    bb2_terminal(["Return read x$7_@0"])
+    bb2_terminal(["Return read x$7_@1"])
   end
 
   %% Jumps
@@ -104,7 +106,7 @@ flowchart TB
 ```javascript
 function foo$0() {
   let x$7 = 1;
-  bb2: for (const i$8 = 0; i$8 < 10; update$3()) {
+  bb2: for (let i$8 = 0; i$8 < 10; i$8 = i$8 + 1, i$8) {
     x$7 = x$7 + 1;
   }
 
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-for.js b/compiler/forget/src/__tests__/fixtures/hir/ssa-for.js
index 950e2450e7..455f279915 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/ssa-for.js
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-for.js
@@ -1,6 +1,6 @@
 function foo() {
   let x = 1;
-  for (let i = 0; i < 10; update()) {
+  for (let i = 0; i < 10; i += 1) {
     x += 1;
   }
   return x;
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-while-no-reassign.expect.md b/compiler/forget/src/__tests__/fixtures/hir/ssa-while-no-reassign.expect.md
index 088e4e6766..2307b9a5b3 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/ssa-while-no-reassign.expect.md
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-while-no-reassign.expect.md
@@ -21,7 +21,7 @@ bb0:
   [2] While test=bb1 loop=bb3 fallthrough=bb2
 bb1:
   predecessor blocks: bb0 bb3
-  [3] Const mutate $6_@1 = 10
+  [3] Const mutate $6_@1[3:6] = 10
   [4] Const mutate $8_@2[4:6] = Binary read x$5_@0 < read $6_@1
   [5] If (read $8_@2) then:bb3 else:bb2 fallthrough=bb2
 bb3:
@@ -34,7 +34,6 @@ bb2:
   [9] Return read x$5_@0
 scope2 [4:6]:
   - dependency: read x$5_@0
-  - dependency: read $6_@1
 scope3 [6:7]:
   - dependency: read x$5_@0
 ```
@@ -52,7 +51,7 @@ flowchart TB
   end
   subgraph bb1
     bb1_instrs["
-      [3] Const mutate $6_@1 = 10
+      [3] Const mutate $6_@1[3:6] = 10
       [4] Const mutate $8_@2[4:6] = Binary read x$5_@0 < read $6_@1
     "]
     bb1_instrs --> bb1_terminal(["If (read $8_@2)"])
diff --git a/compiler/forget/src/__tests__/fixtures/hir/ssa-while.expect.md b/compiler/forget/src/__tests__/fixtures/hir/ssa-while.expect.md
index 8fda351553..32e88277ad 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/ssa-while.expect.md
+++ b/compiler/forget/src/__tests__/fixtures/hir/ssa-while.expect.md
@@ -21,8 +21,8 @@ bb0:
   [2] While test=bb1 loop=bb3 fallthrough=bb2
 bb1:
   predecessor blocks: bb0 bb3
-  [3] Const mutate $6_@1 = 10
-  [4] Const mutate $8_@0[1:9] = Binary read x$5_@0 < read $6_@1
+  [3] Const mutate $6_@0[1:9] = 10
+  [4] Const mutate $8_@0[1:9] = Binary read x$5_@0 < read $6_@0
   [5] If (read $8_@0) then:bb3 else:bb2 fallthrough=bb2
 bb3:
   predecessor blocks: bb1
@@ -48,8 +48,8 @@ flowchart TB
   end
   subgraph bb1
     bb1_instrs["
-      [3] Const mutate $6_@1 = 10
-      [4] Const mutate $8_@0[1:9] = Binary read x$5_@0 < read $6_@1
+      [3] Const mutate $6_@0[1:9] = 10
+      [4] Const mutate $8_@0[1:9] = Binary read x$5_@0 < read $6_@0
     "]
     bb1_instrs --> bb1_terminal(["If (read $8_@0)"])
   end