diff --git a/src/functionObjects/field/streamLine/streamLineBase.C b/src/functionObjects/field/streamLine/streamLineBase.C
index 0c1616d16d4ec4f1fd281e1d9a9c31d889124d01..2a489fdc78ae8e6d2d245e93647011cd02704551 100644
--- a/src/functionObjects/field/streamLine/streamLineBase.C
+++ b/src/functionObjects/field/streamLine/streamLineBase.C
@@ -512,7 +512,7 @@ bool Foam::functionObjects::streamLineBase::read(const dictionary& dict)
     Info<< type() << " " << name() << ":" << nl;
 
     dict.lookup("fields") >> fields_;
-    dict.lookup("U") >> UName_;
+    UName_ = dict.lookupOrDefault<word>("U", "U");
 
     if (findIndex(fields_, UName_) == -1)
     {