diff --git a/src/script_opt/ZAM/AM-Opt.cc b/src/script_opt/ZAM/AM-Opt.cc
index dbb5804a58..cd4a3e6b6f 100644
--- a/src/script_opt/ZAM/AM-Opt.cc
+++ b/src/script_opt/ZAM/AM-Opt.cc
@@ -158,15 +158,15 @@ bool ZAMCompiler::RemoveDeadCode() {
         }
 
         if ( t && t->inst_num > i0->inst_num && (! i1 || t->inst_num <= i1->inst_num) ) {
-            // This is effectively a branch to the next
-            // instruction.  Even if i0 is conditional, there's
-            // no point executing it because regardless of the
-            // outcome of the conditional, we go to the next
-            // successive live instruction (and we don't have
-            // conditionals with side effects).
-            KillInst(i0);
-            did_removal = true;
-            continue;
+            // This is effectively a branch to the next instruction.
+            // We can remove it *unless* the instruction has side effects.
+            // Conditionals don't, but loop-iteration-advancement
+            // instructions do.
+            if ( ! i0->IsLoopIterationAdvancement() ) {
+                KillInst(i0);
+                did_removal = true;
+                continue;
+            }
         }
 
         if ( i0->DoesNotContinue() && i1 && i1->num_labels == 0 ) {
diff --git a/src/script_opt/ZAM/ZInst.cc b/src/script_opt/ZAM/ZInst.cc
index ae9cf7999b..4224576fe1 100644
--- a/src/script_opt/ZAM/ZInst.cc
+++ b/src/script_opt/ZAM/ZInst.cc
@@ -214,6 +214,23 @@ ValPtr ZInst::ConstVal() const {
     return nullptr;
 }
 
+bool ZInst::IsLoopIterationAdvancement() const {
+    switch ( op ) {
+        case OP_NEXT_TABLE_ITER_VV:
+        case OP_NEXT_TABLE_ITER_NO_VARS_VV:
+        case OP_NEXT_TABLE_ITER_VAL_VAR_VVV:
+        case OP_NEXT_TABLE_ITER_VAL_VAR_NO_VARS_VVV:
+        case OP_NEXT_VECTOR_ITER_VVV:
+        case OP_NEXT_VECTOR_BLANK_ITER_VV:
+        case OP_NEXT_VECTOR_ITER_VAL_VAR_VVVV:
+        case OP_NEXT_VECTOR_BLANK_ITER_VAL_VAR_VVV:
+        case OP_NEXT_STRING_ITER_VVV:
+        case OP_NEXT_STRING_BLANK_ITER_VV: return true;
+
+        default: return false;
+    }
+}
+
 string ZInst::ConstDump() const {
     auto v = ConstVal();
 
diff --git a/src/script_opt/ZAM/ZInst.h b/src/script_opt/ZAM/ZInst.h
index 2d58b7ac2e..8e53d39b69 100644
--- a/src/script_opt/ZAM/ZInst.h
+++ b/src/script_opt/ZAM/ZInst.h
@@ -88,6 +88,10 @@ public:
     // Returns nil if this instruction doesn't have an associated constant.
     ValPtr ConstVal() const;
 
+    // Returns true if this instruction represents a form of advancing
+    // a loop iteration, false otherwise.
+    bool IsLoopIterationAdvancement() const;
+
     // Returns a string describing the constant.
     std::string ConstDump() const;