diff --git a/doc/fixes3-7-0.txt b/doc/fixes3-7-0.txt
index 41614da5c..d99e58d97 100644
--- a/doc/fixes3-7-0.txt
+++ b/doc/fixes3-7-0.txt
@@ -1383,6 +1383,7 @@ using '#adjust c d' or '#adjust d c' after splitting slot c via '#adjust Nc d'
 	them even though merging was the intended behavior (the 3.6 change
 	that caused this was intended to avoid collecting other compatible
 	stacks while still merging the two specified ones)
+ring of aggravate monster increases the level difficulty
 
 
 Fixes to 3.7.0-x General Problems Exposed Via git Repository
diff --git a/src/dungeon.c b/src/dungeon.c
index 86b8fb4a2..034d1991f 100644
--- a/src/dungeon.c
+++ b/src/dungeon.c
@@ -2041,6 +2041,9 @@ level_difficulty(void)
              */
 #endif /*0*/
     }
+    /* ring of aggravate monster */
+    if (EAggravate_monster)
+        res += 15;
     return res;
 }