diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 531e3f752..3f73c24a1 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -619,18 +619,18 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
 // typedef std::optional<const std::map<std::string, Value *>> valmap;
 typedef const std::map<std::string, Value *> valmap;
 
-static std::unique_ptr<valmap> map1(const char *name, Value *v) __attribute__((noinline)); 
-std::unique_ptr<valmap> map1(const char *name, Value *v)
+static valmap* map1(const char *name, Value *v) __attribute__((noinline)); 
+valmap* map1(const char *name, Value *v)
 {
     // return new valmap({{name, v}}); 
-    return std::unique_ptr<valmap>(new valmap({{name, v}})); 
+    return new valmap({{name, v}}); 
 }
 
 
-static std::unique_ptr<valmap> map2(const char *name1, Value *v1, const char *name2, Value *v2) __attribute__((noinline)); 
-std::unique_ptr<valmap> map2(const char *name1, Value *v1, const char *name2, Value *v2)
+static valmap* map2(const char *name1, Value *v1, const char *name2, Value *v2) __attribute__((noinline)); 
+valmap* map2(const char *name1, Value *v1, const char *name2, Value *v2)
 {
-    return std::unique_ptr<valmap>(new valmap({{name1, v1}, {name2, v2}})); 
+    return new valmap({{name1, v1}, {name2, v2}}); 
 }
 
 /* Every "format" object (even temporary) takes up a few hundred bytes
@@ -673,8 +673,9 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const
     });
 }
 
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, std::unique_ptr<valmap> env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, valmap* env))
 {
+    auto delenv = std::unique_ptr<valmap>(env);
     auto error = TypeError({
         .msg = hintfmt(s),
         .errPos = pos
@@ -685,8 +686,9 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, std::
     throw error;
 }
 
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, std::unique_ptr<valmap> env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, valmap* env))
 {
+    auto delenv = std::unique_ptr<valmap>(env);
     auto error = TypeError({
         .msg = hintfmt(s, v),
         .errPos = pos
@@ -697,8 +699,9 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
     throw error;
 }
 
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, std::unique_ptr<valmap> env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, valmap* env))
 {
+    auto delenv = std::unique_ptr<valmap>(env);
     auto error = TypeError({
         .msg = hintfmt(s, fun.showNamePos(), s2),
         .errPos = pos
@@ -727,7 +730,7 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
     });
 }
 
-LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, std::unique_ptr<valmap> env))
+LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, valmap* env))
 {
     auto error = MissingArgumentError({
         .msg = hintfmt(s, s1),