diff --git a/CHANGES b/CHANGES
index 15d418df6d..cdadc67fde 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,22 @@
+8.0.0-dev.622 | 2025-07-09 15:10:03 -0700
+
+  * ZAM optimizer fix for += / -= set operations (Vern Paxson, Corelight)
+
+  * Bump `spicy-format` pre-commit hook (Benjamin Bannier, Corelight)
+
+    pre-commit ignores Cargo.lock files for Rust projects, so any movement
+    in a Rust project's dependencies can break a hook, even if no code in
+    the hook changed. I have tried to work with upstream on a fix, but they
+    basically told me they weren't interested and to get lost.
+
+    This bumps the `spicy-format` pre-commit hook to a new version which
+    explicitly deals with bumps of its dependencies. Having to do this
+    semi-regularly is not fun, and ideally somebody interested in using this
+    hook would help set up infrastructure in the hook so it just pulls
+    pre-built binaries. This is not directly supported by pre-commit, but
+    many projects work around this by declaring a Python module which then
+    pulls pre-build binaries which already exist for spicy-format.
+
 8.0.0-dev.618 | 2025-07-08 17:45:16 -0700
 
   * Clarify the cookie field's origin in the RDP log. (Christian Kreibich, Corelight)
diff --git a/VERSION b/VERSION
index 284ce4b805..88baf037c2 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-8.0.0-dev.618
+8.0.0-dev.622
diff --git a/src/script_opt/Expr.cc b/src/script_opt/Expr.cc
index 159d0107e7..cb2927c6de 100644
--- a/src/script_opt/Expr.cc
+++ b/src/script_opt/Expr.cc
@@ -767,6 +767,9 @@ bool AddToExpr::IsReduced(Reducer* c) const {
 }
 
 ExprPtr AddToExpr::Reduce(Reducer* c, StmtPtr& red_stmt) {
+    if ( c->Optimizing() )
+        op2 = c->UpdateExpr(op2);
+
     auto tag = op1->GetType()->Tag();
 
     switch ( tag ) {
@@ -869,6 +872,9 @@ bool RemoveFromExpr::IsReduced(Reducer* c) const {
 }
 
 ExprPtr RemoveFromExpr::Reduce(Reducer* c, StmtPtr& red_stmt) {
+    if ( c->Optimizing() )
+        op2 = c->UpdateExpr(op2);
+
     if ( op1->GetType()->Tag() == TYPE_TABLE ) {
         StmtPtr red_stmt1;
         StmtPtr red_stmt2;
diff --git a/testing/btest/Baseline/opt.regress-set-op-opt/output b/testing/btest/Baseline/opt.regress-set-op-opt/output
new file mode 100644
index 0000000000..6102e32795
--- /dev/null
+++ b/testing/btest/Baseline/opt.regress-set-op-opt/output
@@ -0,0 +1,4 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+[my_set={
+
+}]
diff --git a/testing/btest/opt/regress-set-op-opt.zeek b/testing/btest/opt/regress-set-op-opt.zeek
new file mode 100644
index 0000000000..8e11e0725c
--- /dev/null
+++ b/testing/btest/opt/regress-set-op-opt.zeek
@@ -0,0 +1,20 @@
+# @TEST-DOC: Regression test for ZAM optimizer mis-transforming set +=/-= ops
+# @TEST-REQUIRES: test "${ZEEK_USE_CPP}" != "1"
+# @TEST-EXEC: zeek -b -O ZAM %INPUT >output
+# @TEST-EXEC: btest-diff output
+
+type R: record {
+	my_set: set[string];
+};
+
+event zeek_init()
+	{
+	local r1 = R();
+	local r2 = R();
+
+	if ( |r1$my_set| > 0 )
+		print T;
+
+	r2$my_set += r1$my_set;
+	print r2;
+	}