diff --git a/MantidPlot/src/ProjectRecovery.cpp b/MantidPlot/src/ProjectRecovery.cpp
index b5f112c34d08988843259323687746561d523a26..94802be21c3b56ccd2cadac55f1ebcaf898b3290 100644
--- a/MantidPlot/src/ProjectRecovery.cpp
+++ b/MantidPlot/src/ProjectRecovery.cpp
@@ -126,7 +126,7 @@ getRecoveryFolderCheckpoints(const std::string &recoveryFolderPath) {
 
 std::string removeInvalidFilenameChars(std::string s) {
   // NTFS is most restrictive, so blacklist on this
-  std::string blacklistChars{":*?<>|/\"\\"};
+  std::string blacklistChars{"#:*?<>|/\"\\"};
   boost::remove_erase_if(s, boost::is_any_of(blacklistChars));
   return s;
 }