3 files changed, 12 insertions, 5 deletions
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index f95df5e4d6fb..eb1d8d432c69 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -902,12 +902,18 @@ string EvalState::forceString(Value & v)
 }
 
 
-string EvalState::forceString(Value & v, PathSet & context)
+void copyContext(const Value & v, PathSet & context)
 {
-    string s = forceString(v);
     if (v.string.context)
         for (const char * * p = v.string.context; *p; ++p) 
             context.insert(*p);
+}
+
+
+string EvalState::forceString(Value & v, PathSet & context)
+{
+    string s = forceString(v);
+    copyContext(v, context);
     return s;
 }
 
@@ -938,9 +944,7 @@ string EvalState::coerceToString(Value & v, PathSet & context,
     string s;
 
     if (v.type == tString) {
-        if (v.string.context) 
-            for (const char * * p = v.string.context; *p; ++p) 
-                context.insert(*p);
+        copyContext(v, context);
         return v.string.s;
     }
 
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 65c689a509d9..0cdf0b28300f 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -161,6 +161,8 @@ void mkString(Value & v, const char * s);
 void mkString(Value & v, const string & s, const PathSet & context = PathSet());
 void mkPath(Value & v, const char * s);
 
+void copyContext(const Value & v, PathSet & context);
+
 
 typedef std::map<Path, Hash> DrvHashes;
 
diff --git a/src/libexpr/value-to-xml.cc b/src/libexpr/value-to-xml.cc
index e751fd300fdb..8955a8a33931 100644
--- a/src/libexpr/value-to-xml.cc
+++ b/src/libexpr/value-to-xml.cc
@@ -69,6 +69,7 @@ static void printValueAsXML(EvalState & state, bool strict, bool location,
 
         case tString:
             /* !!! show the context? */
+            copyContext(v, context);
             doc.writeEmptyElement("string", singletonAttrs("value", v.string.s));
             break;