diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 9b0df92388..94410e2bda 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -942,6 +942,14 @@ static Expr prim_stringLength(EvalState & state, const ATermVector & args)
 }
 
 
+static Expr prim_unsafeDiscardStringContext(EvalState & state, const ATermVector & args)
+{
+    PathSet context;
+    string s = coerceToString(state, args[0], context);
+    return makeStr(s, PathSet());
+}
+
+
 /*************************************************************
  * Primop registration
  *************************************************************/
@@ -1009,6 +1017,8 @@ void EvalState::addPrimOps()
     addPrimOp("toString", 1, prim_toString);
     addPrimOp("__substring", 3, prim_substring);
     addPrimOp("__stringLength", 1, prim_stringLength);
+    addPrimOp("__unsafeDiscardStringContext", 1, prim_unsafeDiscardStringContext);
+    
 }
 
 
diff --git a/tests/lang/eval-okay-context.exp b/tests/lang/eval-okay-context.exp
new file mode 100644
index 0000000000..95a9936542
--- /dev/null
+++ b/tests/lang/eval-okay-context.exp
@@ -0,0 +1 @@
+Str("foo eval-okay-context.nix bar",[])
diff --git a/tests/lang/eval-okay-context.nix b/tests/lang/eval-okay-context.nix
new file mode 100644
index 0000000000..b3f1748975
--- /dev/null
+++ b/tests/lang/eval-okay-context.nix
@@ -0,0 +1,6 @@
+let s = "foo ${builtins.substring 33 100 (baseNameOf ./eval-okay-context.nix)} bar";
+in
+  if s == "foo eval-okay-context.nix bar"
+  then abort "context not discarded"
+  else builtins.unsafeDiscardStringContext s
+