diff --git a/src/Expr.cc b/src/Expr.cc
index 9f333c641e..cf4e52f3cf 100644
--- a/src/Expr.cc
+++ b/src/Expr.cc
@@ -2545,7 +2545,7 @@ ValPtr IndexExpr::Fold(Val* v1, Val* v2) const {
 
         case TYPE_TABLE:
             if ( is_pattern_table )
-                return v1->AsTableVal()->LookupPattern(v2->AsListVal()->Idx(0)->AsStringVal());
+                return v1->AsTableVal()->LookupPattern({NewRef{}, v2->AsListVal()->Idx(0)->AsStringVal()});
 
             v = v1->AsTableVal()->FindOrDefault({NewRef{}, v2});
             break;
diff --git a/src/Val.cc b/src/Val.cc
index 73bfd2dce7..d8bd8d1897 100644
--- a/src/Val.cc
+++ b/src/Val.cc
@@ -1440,7 +1440,7 @@ public:
 
     void Clear() { matcher.reset(); }
 
-    VectorValPtr Lookup(const StringVal* s);
+    VectorValPtr Lookup(const StringValPtr& s);
 
 private:
     void Build();
@@ -1463,7 +1463,7 @@ private:
     std::vector<ValPtr> matcher_yields;
 };
 
-VectorValPtr detail::TablePatternMatcher::Lookup(const StringVal* s) {
+VectorValPtr detail::TablePatternMatcher::Lookup(const StringValPtr& s) {
     auto results = make_intrusive<VectorVal>(vtype);
 
     if ( ! matcher ) {
@@ -2016,7 +2016,7 @@ TableValPtr TableVal::LookupSubnetValues(const SubNetVal* search) {
     return nt;
 }
 
-VectorValPtr TableVal::LookupPattern(const StringVal* s) {
+VectorValPtr TableVal::LookupPattern(const StringValPtr& s) {
     if ( ! pattern_matcher )
         reporter->InternalError("LookupPattern called on wrong table type");
 
diff --git a/src/Val.h b/src/Val.h
index 3b5176849b..9f201be1b2 100644
--- a/src/Val.h
+++ b/src/Val.h
@@ -867,7 +867,7 @@ public:
     // For a table[pattern], return a vector of all yields matching
     // the given string.
     // Causes an internal error if called for any other kind of table.
-    VectorValPtr LookupPattern(const StringVal* s);
+    VectorValPtr LookupPattern(const StringValPtr& s);
 
     // Sets the timestamp for the given index to network time.
     // Returns false if index does not exist.
diff --git a/src/script_opt/CPP/RuntimeOps.cc b/src/script_opt/CPP/RuntimeOps.cc
index 273b77b315..ae2b9c7744 100644
--- a/src/script_opt/CPP/RuntimeOps.cc
+++ b/src/script_opt/CPP/RuntimeOps.cc
@@ -45,7 +45,7 @@ ValPtr index_table__CPP(const TableValPtr& t, vector<ValPtr> indices) {
 }
 
 ValPtr index_patstr_table__CPP(const TableValPtr& t, vector<ValPtr> indices) {
-    return t->LookupPattern(indices[0]->AsStringVal());
+    return t->LookupPattern(cast_intrusive<StringVal>(indices[0]));
 }
 
 ValPtr index_vec__CPP(const VectorValPtr& vec, int index) {
diff --git a/src/script_opt/ZAM/Ops.in b/src/script_opt/ZAM/Ops.in
index 87b820177f..3ffbeb6462 100644
--- a/src/script_opt/ZAM/Ops.in
+++ b/src/script_opt/ZAM/Ops.in
@@ -1061,7 +1061,7 @@ internal-op When-PatStr-Index
 type VV
 eval	auto args = z.aux->ToListVal(frame);
 	auto arg0 = args->Idx(0);
-	auto v = frame[z.v2].table_val->LookupPattern(arg0->AsStringVal());
+	auto v = frame[z.v2].table_val->LookupPattern({NewRef{}, arg0->AsStringVal()});
 	if ( IndexExprWhen::evaluating > 0 )
 		IndexExprWhen::results.emplace_back(v);
 	AssignV1(BuildVal(v, z.t))
@@ -1081,12 +1081,12 @@ eval	EvalTableIndex(z.c.ToVal(z.t))
 internal-assignment-op Table-PatStr-Index1
 type VVV
 assign-val v
-eval	auto v = frame[z.v2].table_val->LookupPattern(frame[z.v3].AsString());
+eval	auto v = frame[z.v2].table_val->LookupPattern({NewRef{}, frame[z.v3].AsString()});
 
 internal-assignment-op Table-PatStr-Index1
 type VVC
 assign-val v
-eval	auto v = frame[z.v2].table_val->LookupPattern(z.c.AsString());
+eval	auto v = frame[z.v2].table_val->LookupPattern({NewRef{}, z.c.AsString()});
 
 # This version is for a variable v3.
 internal-op Index-String