diff --git a/src/libexpr/lexer.l b/src/libexpr/lexer.l
index 9a35dd594..df2cbd06f 100644
--- a/src/libexpr/lexer.l
+++ b/src/libexpr/lexer.l
@@ -36,9 +36,6 @@ static inline PosIdx makeCurPos(const YYLTYPE & loc, ParseData * data)
 
 #define CUR_POS makeCurPos(*yylloc, data)
 
-// backup to recover from yyless(0)
-thread_local YYLTYPE prev_yylloc;
-
 static void initLoc(YYLTYPE * loc)
 {
     loc->first_line = loc->last_line = 1;
@@ -47,7 +44,7 @@ static void initLoc(YYLTYPE * loc)
 
 static void adjustLoc(YYLTYPE * loc, const char * s, size_t len)
 {
-    prev_yylloc = *loc;
+    loc->stash();
 
     loc->first_line = loc->last_line;
     loc->first_column = loc->last_column;
@@ -231,7 +228,7 @@ or          { return OR_KW; }
 {HPATH_START}\$\{ {
   PUSH_STATE(PATH_START);
   yyless(0);
-  *yylloc = prev_yylloc;
+  yylloc->unstash();
 }
 
 <PATH_START>{PATH_SEG} {
@@ -287,7 +284,7 @@ or          { return OR_KW; }
      context (it may be ')', ';', or something of that sort) */
   POP_STATE();
   yyless(0);
-  *yylloc = prev_yylloc;
+  yylloc->unstash();
   return PATH_END;
 }
 
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 16ad8af2e..b331776f0 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -28,6 +28,31 @@
 
 namespace nix {
 
+#define YYLTYPE ::nix::ParserLocation
+    struct ParserLocation
+    {
+        int first_line, first_column;
+        int last_line, last_column;
+
+        // backup to recover from yyless(0)
+        int stashed_first_line, stashed_first_column;
+        int stashed_last_line, stashed_last_column;
+
+        void stash() {
+          stashed_first_line = first_line;
+          stashed_first_column = first_column;
+          stashed_last_line = last_line;
+          stashed_last_column = last_column;
+        }
+
+        void unstash() {
+          first_line = stashed_first_line;
+          first_column = stashed_first_column;
+          last_line = stashed_last_line;
+          last_column = stashed_last_column;
+        }
+    };
+
     struct ParseData
     {
         EvalState & state;