diff --git a/src/script_opt/Stmt.cc b/src/script_opt/Stmt.cc
index 6747ceb8c3..d1eebfeccd 100644
--- a/src/script_opt/Stmt.cc
+++ b/src/script_opt/Stmt.cc
@@ -904,7 +904,7 @@ bool StmtList::SimplifyChain(unsigned int start, unsigned int end, std::vector<S
     OpChain add_chains;
     std::set<const Stmt*> chain_stmts;
 
-    for ( int i = start; i <= end; ++i ) {
+    for ( auto i = start; i <= end; ++i ) {
         auto& s = stmts[i];
         chain_stmts.insert(s.get());
         UpdateAssignmentChains(s, assign_chains, add_chains);
diff --git a/src/script_opt/ZAM/Ops.in b/src/script_opt/ZAM/Ops.in
index 05d3213b32..fd90ee4b8c 100644
--- a/src/script_opt/ZAM/Ops.in
+++ b/src/script_opt/ZAM/Ops.in
@@ -1288,7 +1288,7 @@ op1-read
 type VV
 eval	SetUpRecFieldOps()
 	auto is_managed = aux->is_managed;
-	for ( auto i = 0; i < n; ++i )
+	for ( size_t i = 0U; i < n; ++i )
 		if ( is_managed[i] )
 			{
 			auto& lhs_i = lhs->RawOptField(lhs_map[i]);