diff --git a/src/support/FileName.cpp b/src/support/FileName.cpp
index bd1aac9aab..1d114f8114 100644
--- a/src/support/FileName.cpp
+++ b/src/support/FileName.cpp
@@ -309,7 +309,7 @@ bool FileName::isWritable() const
 bool FileName::isDirWritable() const
 {
 	LYXERR(Debug::FILES, "isDirWriteable: " << *this);
-	FileName const tmpfl = FileName::tempName(absFilename() + "/lyxwritetest");
+	FileName const tmpfl = FileName::tempName(absFilename() + "lyxwritetest");
 	return !tmpfl.empty();
 }