diff --git a/src/init.cpp b/src/init.cpp
index 1dda35e1c..f5ea421c7 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -377,6 +377,7 @@ std::string HelpMessage(HelpMessageMode mode)
     strUsage += HelpMessageOpt("-exportdir=<dir>", _("Specify directory to be used when exporting data"));
     strUsage += HelpMessageOpt("-dbcache=<n>", strprintf(_("Set database cache size in megabytes (%d to %d, default: %d)"), nMinDbCache, nMaxDbCache, nDefaultDbCache));
     strUsage += HelpMessageOpt("-loadblock=<file>", _("Imports blocks from external blk000??.dat file") + " " + _("on startup"));
+    strUsage += HelpMessageOpt("-maxdebugfilesize=<n>", strprintf(_("Set the max size of the debug.log file (default: %u)"), 15));
     strUsage += HelpMessageOpt("-maxorphantx=<n>", strprintf(_("Keep at most <n> unconnectable transactions in memory (default: %u)"), DEFAULT_MAX_ORPHAN_TRANSACTIONS));
     strUsage += HelpMessageOpt("-mempooltxinputlimit=<n>", _("[DEPRECATED/IGNORED] Set the maximum number of transparent inputs in a transaction that the mempool will accept (default: 0 = no limit applied)"));
     strUsage += HelpMessageOpt("-par=<n>", strprintf(_("Set the number of script verification threads (%u to %d, 0 = auto, <0 = leave that many cores free, default: %d)"),