diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 34a212aa4..f3e8a34bd 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -144,8 +144,8 @@ public:
     Expr * parseExprFromFile(const Path & path, StaticEnv & staticEnv);
 
     /* Parse a Nix expression from the specified string. */
-    Expr * parseExprFromString(const string & s, const Path & basePath, StaticEnv & staticEnv);
-    Expr * parseExprFromString(const string & s, const Path & basePath);
+    Expr * parseExprFromString(std::string_view s, const Path & basePath, StaticEnv & staticEnv);
+    Expr * parseExprFromString(std::string_view s, const Path & basePath);
 
     Expr * parseStdin();
 
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index afa1fd439..9c769e803 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -611,13 +611,13 @@ Expr * EvalState::parseExprFromFile(const Path & path, StaticEnv & staticEnv)
 }
 
 
-Expr * EvalState::parseExprFromString(const string & s, const Path & basePath, StaticEnv & staticEnv)
+Expr * EvalState::parseExprFromString(std::string_view s, const Path & basePath, StaticEnv & staticEnv)
 {
-    return parse(s.c_str(), "(string)", basePath, staticEnv);
+    return parse(s.data(), "(string)", basePath, staticEnv);
 }
 
 
-Expr * EvalState::parseExprFromString(const string & s, const Path & basePath)
+Expr * EvalState::parseExprFromString(std::string_view s, const Path & basePath)
 {
     return parseExprFromString(s, basePath, staticBaseEnv);
 }