Index: subr_blist.c
===================================================================
--- subr_blist.c
+++ subr_blist.c
@@ -648,6 +648,18 @@
 				return (avail);
 			}
 			maxcount = imin(avail, maxcount);
+			if (maxcount % BLIST_BMAP_RADIX == 0) {
+				/*
+				 * There was no next leaf.  Back scan up to
+				 * last leaf.
+				 */
+				--scan;
+				while (radix != BLIST_BMAP_RADIX) {
+					radix /= BLIST_META_RADIX;
+					--scan;
+				}
+				blk -= BLIST_BMAP_RADIX;
+			}
 		}
 	}