diff --git a/src/script_opt/Stmt.cc b/src/script_opt/Stmt.cc
index d1eebfeccd..b89b44a264 100644
--- a/src/script_opt/Stmt.cc
+++ b/src/script_opt/Stmt.cc
@@ -904,6 +904,10 @@ bool StmtList::SimplifyChain(unsigned int start, unsigned int end, std::vector<S
     OpChain add_chains;
     std::set<const Stmt*> chain_stmts;
 
+    static bool skip_chains = getenv("ZAM_SKIP_CHAINS");
+    if ( skip_chains )
+        return false;
+
     for ( auto i = start; i <= end; ++i ) {
         auto& s = stmts[i];
         chain_stmts.insert(s.get());
diff --git a/src/script_opt/ZAM/Expr.cc b/src/script_opt/ZAM/Expr.cc
index aa01b4728b..81b09c5fdc 100644
--- a/src/script_opt/ZAM/Expr.cc
+++ b/src/script_opt/ZAM/Expr.cc
@@ -242,7 +242,7 @@ const ZAMStmt ZAMCompiler::CompileRecFieldUpdates(const RecordFieldUpdates* e) {
 
     std::set<TypeTag> field_tags;
 
-    bool is_managed = false;
+    size_t num_managed = 0;
 
     for ( auto i : rhs_map ) {
         auto rt = rhs->GetType()->AsRecordType();
@@ -251,7 +251,7 @@ const ZAMStmt ZAMCompiler::CompileRecFieldUpdates(const RecordFieldUpdates* e) {
 
         if ( ZVal::IsManagedType(rt_ft_i) ) {
             aux->is_managed.push_back(true);
-            is_managed = true;
+            ++num_managed;
         }
         else
             // This will only be needed if is_managed winds up being true,
@@ -269,8 +269,14 @@ const ZAMStmt ZAMCompiler::CompileRecFieldUpdates(const RecordFieldUpdates* e) {
 
     ZOp op;
 
-    if ( e->Tag() == EXPR_REC_ASSIGN_FIELDS )
-        op = is_managed ? OP_REC_ASSIGN_FIELDS_MANAGED_VV : OP_REC_ASSIGN_FIELDS_VV;
+    if ( e->Tag() == EXPR_REC_ASSIGN_FIELDS ) {
+        if ( num_managed == rhs_map.size() )
+            op = OP_REC_ASSIGN_FIELDS_ALL_MANAGED_VV;
+        else if ( num_managed > 0 )
+            op = OP_REC_ASSIGN_FIELDS_MANAGED_VV;
+        else
+            op = OP_REC_ASSIGN_FIELDS_VV;
+    }
 
     else if ( homogeneous ) {
         if ( field_tags.count(TYPE_DOUBLE) > 0 )
diff --git a/src/script_opt/ZAM/Ops.in b/src/script_opt/ZAM/Ops.in
index fd90ee4b8c..4a6c672f57 100644
--- a/src/script_opt/ZAM/Ops.in
+++ b/src/script_opt/ZAM/Ops.in
@@ -1301,6 +1301,20 @@ eval	SetUpRecFieldOps()
 		else
 			lhs->RawOptField(lhs_map[i]) = rhs->RawField(rhs_map[i]);
 
+op Rec-Assign-Fields-All-Managed
+op1-read
+type VV
+eval	SetUpRecFieldOps()
+	for ( size_t i = 0U; i < n; ++i )
+		{
+		auto& lhs_i = lhs->RawOptField(lhs_map[i]);
+		auto rhs_i = rhs->RawField(rhs_map[i]);
+		zeek::Ref(rhs_i.ManagedVal());
+		if ( lhs_i )
+			ZVal::DeleteManagedType(*lhs_i);
+		lhs_i = rhs_i;
+		}
+
 op Rec-Add-Int-Fields
 op1-read
 type VV