diff --git a/doc/manual/rl-next/formal-order.md b/doc/manual/rl-next/formal-order.md
new file mode 100644
index 000000000..12628e318
--- /dev/null
+++ b/doc/manual/rl-next/formal-order.md
@@ -0,0 +1,7 @@
+---
+synopsis: consistent order of lambda formals in printed expressions
+prs: 9874
+---
+
+Always print lambda formals in lexicographic order rather than the internal, creation-time based symbol order.
+This makes printed formals independent of the context they appear in.
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 3bcd35fef..c591916e3 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -147,7 +147,10 @@ void ExprLambda::show(const SymbolTable & symbols, std::ostream & str) const
     if (hasFormals()) {
         str << "{ ";
         bool first = true;
-        for (auto & i : formals->formals) {
+        // the natural Symbol ordering is by creation time, which can lead to the
+        // same expression being printed in two different ways depending on its
+        // context. always use lexicographic ordering to avoid this.
+        for (auto & i : formals->lexicographicOrder(symbols)) {
             if (first) first = false; else str << ", ";
             str << symbols[i.name];
             if (i.def) {
diff --git a/tests/functional/lang/parse-okay-subversion.exp b/tests/functional/lang/parse-okay-subversion.exp
index 2303932c4..32fbba3c5 100644
--- a/tests/functional/lang/parse-okay-subversion.exp
+++ b/tests/functional/lang/parse-okay-subversion.exp
@@ -1 +1 @@
-({ fetchurl, localServer ? false, httpServer ? false, sslSupport ? false, pythonBindings ? false, javaSwigBindings ? false, javahlBindings ? false, stdenv, openssl ? null, httpd ? null, db4 ? null, expat, swig ? null, j2sdk ? null }: assert (expat != null); assert (localServer -> (db4 != null)); assert (httpServer -> ((httpd != null) && ((httpd).expat == expat))); assert (sslSupport -> ((openssl != null) && (httpServer -> ((httpd).openssl == openssl)))); assert (pythonBindings -> ((swig != null) && (swig).pythonSupport)); assert (javaSwigBindings -> ((swig != null) && (swig).javaSupport)); assert (javahlBindings -> (j2sdk != null)); ((stdenv).mkDerivation { inherit expat httpServer javaSwigBindings javahlBindings localServer pythonBindings sslSupport; builder = /foo/bar; db4 = (if localServer then db4 else null); httpd = (if httpServer then httpd else null); j2sdk = (if javaSwigBindings then (swig).j2sdk else (if javahlBindings then j2sdk else null)); name = "subversion-1.1.1"; openssl = (if sslSupport then openssl else null); patches = (if javahlBindings then [ (/javahl.patch) ] else [ ]); python = (if pythonBindings then (swig).python else null); src = (fetchurl { md5 = "a180c3fe91680389c210c99def54d9e0"; url = "http://subversion.tigris.org/tarballs/subversion-1.1.1.tar.bz2"; }); swig = (if (pythonBindings || javaSwigBindings) then swig else null); }))
+({ db4 ? null, expat, fetchurl, httpServer ? false, httpd ? null, j2sdk ? null, javaSwigBindings ? false, javahlBindings ? false, localServer ? false, openssl ? null, pythonBindings ? false, sslSupport ? false, stdenv, swig ? null }: assert (expat != null); assert (localServer -> (db4 != null)); assert (httpServer -> ((httpd != null) && ((httpd).expat == expat))); assert (sslSupport -> ((openssl != null) && (httpServer -> ((httpd).openssl == openssl)))); assert (pythonBindings -> ((swig != null) && (swig).pythonSupport)); assert (javaSwigBindings -> ((swig != null) && (swig).javaSupport)); assert (javahlBindings -> (j2sdk != null)); ((stdenv).mkDerivation { inherit expat httpServer javaSwigBindings javahlBindings localServer pythonBindings sslSupport; builder = /foo/bar; db4 = (if localServer then db4 else null); httpd = (if httpServer then httpd else null); j2sdk = (if javaSwigBindings then (swig).j2sdk else (if javahlBindings then j2sdk else null)); name = "subversion-1.1.1"; openssl = (if sslSupport then openssl else null); patches = (if javahlBindings then [ (/javahl.patch) ] else [ ]); python = (if pythonBindings then (swig).python else null); src = (fetchurl { md5 = "a180c3fe91680389c210c99def54d9e0"; url = "http://subversion.tigris.org/tarballs/subversion-1.1.1.tar.bz2"; }); swig = (if (pythonBindings || javaSwigBindings) then swig else null); }))