diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index ca0eec6e3..659b97658 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -772,7 +772,7 @@ void printEnvBindings(const SymbolTable & st, const Expr & expr, const Env & env
         printEnvBindings(st, *expr.staticEnv.get(), env, 0);
 }
 
-void mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env, valmap & vm)
+void mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env, ValMap & vm)
 {
     // add bindings for the next level up first, so that the bindings for this level
     // override the higher levels.
@@ -795,9 +795,9 @@ void mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const En
     }
 }
 
-std::unique_ptr<valmap> mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env)
+std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env)
 {
-    auto vm = std::make_unique<valmap>();
+    auto vm = std::make_unique<ValMap>();
     mapStaticEnvBindings(st, se, env, *vm);
     return vm;
 }
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index f3852e248..22f034e27 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -37,7 +37,7 @@ struct PrimOp
     const char * doc = nullptr;
 };
 
-typedef std::map<std::string, Value *> valmap;
+typedef std::map<std::string, Value *> ValMap;
 
 struct Env
 {
@@ -47,7 +47,7 @@ struct Env
     Value * values[0];
 };
 
-std::unique_ptr<valmap> mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env);
+std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env);
 
 void copyContext(const Value & v, PathSet & context);