diff --git a/doc/fixes37.0 b/doc/fixes37.0
index 0e40ac4ac..0096e62df 100644
--- a/doc/fixes37.0
+++ b/doc/fixes37.0
@@ -1315,6 +1315,7 @@ MAX_RADIUS defines the outer bound of the radius table, so leave it at 15
 variable attknum was declared without initialization, and was used in
 	find_roll_to_hit() (pr #615 by argrath)
 check for NULL lua_State before calling lua_close() (pr #616 by argrath)
+use %lu, not %d, in format string in timer_sanity_check() (pr #617 by argrath)
 
 
 Code Cleanup and Reorganization
diff --git a/src/timeout.c b/src/timeout.c
index 630b1b434..fec6a0c33 100644
--- a/src/timeout.c
+++ b/src/timeout.c
@@ -1874,10 +1874,10 @@ timer_sanity_check(void)
                   y = (xchar) (where & 0xFFFF);
 
             if (!isok(x, y)) {
-                impossible("timer sanity: spot timer %d at <%d,%d>",
+                impossible("timer sanity: spot timer %lu at <%d,%d>",
                            curr->tid, x, y);
             } else if (curr->func_index == MELT_ICE_AWAY && !is_ice(x, y)) {
-                impossible("timer sanity: melt timer %d on non-ice %d <%d,%d>",
+                impossible("timer sanity: melt timer %lu on non-ice %d <%d,%d>",
                            curr->tid, levl[x][y].typ, x, y);
             }
         }