diff --git a/auxil/gen-zam b/auxil/gen-zam
index ed44de9c43..21ba218d2e 160000
--- a/auxil/gen-zam
+++ b/auxil/gen-zam
@@ -1 +1 @@
-Subproject commit ed44de9c43ad84fbcf42176719b7a985f538cc4d
+Subproject commit 21ba218d2ed7ec27ef009897e9c83576106a85ae
diff --git a/src/script_opt/ZAM/AM-Opt.cc b/src/script_opt/ZAM/AM-Opt.cc
index 3ee2eb2d19..697235018a 100644
--- a/src/script_opt/ZAM/AM-Opt.cc
+++ b/src/script_opt/ZAM/AM-Opt.cc
@@ -303,7 +303,7 @@ bool ZAMCompiler::PruneUnused() {
         if ( assignmentless_op.count(inst->op) == 0 )
             reporter->InternalError("inconsistency in re-flavoring instruction with side effects");
 
-        inst->op_type = assignmentless_op_type[inst->op];
+        inst->op_type = assignmentless_op_class[inst->op];
         inst->op = assignmentless_op[inst->op];
 
         inst->v1 = inst->v2;
diff --git a/src/script_opt/ZAM/OPs/README.txt b/src/script_opt/ZAM/OPs/README.txt
index bc1e42a0d5..adc2ef4a7e 100644
--- a/src/script_opt/ZAM/OPs/README.txt
+++ b/src/script_opt/ZAM/OPs/README.txt
@@ -145,6 +145,16 @@
 # 		all of possible values not explicitly listed (used in
 # 		conjunction with eval-type - see below)
 #
+#	op-types	similar to op-type, but lists a type for each operand
+#			(including assignment target)
+#
+#		Note that these types collectively apply to each instance of
+#		an operation, whereas listing multiple "op-type" types
+#		iterates through those one-at-a-time in turn (and generally
+#		the point is that the each type applies to *all* operands,
+#		rather than a per-operand list). Given that, the two are
+#		incompatible.
+#
 # 	eval	specifies a block of C++ code used to evaluation the
 # 		execution of the instruction.  The block begins with the
 # 		remainder of the "eval" line and continues until either a
diff --git a/src/script_opt/ZAM/ZInst.h b/src/script_opt/ZAM/ZInst.h
index 4c62523e85..19db6d75ef 100644
--- a/src/script_opt/ZAM/ZInst.h
+++ b/src/script_opt/ZAM/ZInst.h
@@ -551,8 +551,8 @@ extern std::unordered_map<ZOp, std::unordered_map<TypeTag, ZOp>> assignment_flav
 // value is superfluous.
 extern std::unordered_map<ZOp, ZOp> assignmentless_op;
 
-// Maps flavorful assignments to what op-type their non-assignment
+// Maps flavorful assignments to what operand class their non-assignment
 // counterpart uses.
-extern std::unordered_map<ZOp, ZAMOpType> assignmentless_op_type;
+extern std::unordered_map<ZOp, ZAMOpType> assignmentless_op_class;
 
 } // namespace zeek::detail
diff --git a/src/script_opt/ZAM/ZOp.cc b/src/script_opt/ZAM/ZOp.cc
index 161276f2cc..d91ad8b713 100644
--- a/src/script_opt/ZAM/ZOp.cc
+++ b/src/script_opt/ZAM/ZOp.cc
@@ -57,7 +57,7 @@ bool op_side_effects[] = {
 
 std::unordered_map<ZOp, std::unordered_map<TypeTag, ZOp>> assignment_flavor;
 std::unordered_map<ZOp, ZOp> assignmentless_op;
-std::unordered_map<ZOp, ZAMOpType> assignmentless_op_type;
+std::unordered_map<ZOp, ZAMOpType> assignmentless_op_class;
 
 ZOp AssignmentFlavor(ZOp orig, TypeTag tag, bool strict) {
     static bool did_init = false;