diff --git a/mysql-test/r/win.result b/mysql-test/r/win.result
index 019cfd6115d3a..081aaedd32354 100644
--- a/mysql-test/r/win.result
+++ b/mysql-test/r/win.result
@@ -3843,5 +3843,12 @@ ROW_NUMBER() OVER w2
 5
 DROP TABLE t1;
 #
+# MDEV-18916: crash in Window_spec::print_partition() with decimals
+#
+SELECT cast((rank() over w1) as decimal (53,56));
+ERROR 42000: Too big scale 56 specified for 'rank() over w1'. Maximum is 38
+SELECT cast((rank() over w1) as decimal (53,30));
+ERROR HY000: Window specification with name 'w1' is not defined
+#
 # End of 10.2 tests
 #
diff --git a/mysql-test/t/win.test b/mysql-test/t/win.test
index deed7de2d23a9..b749b23508282 100644
--- a/mysql-test/t/win.test
+++ b/mysql-test/t/win.test
@@ -2497,6 +2497,15 @@ SELECT a,b FROM t1 WINDOW w2 AS (PARTITION BY -1,1,0,2,3,4);
 SELECT ROW_NUMBER() OVER w2 FROM t1 WINDOW w2 AS (PARTITION BY -1,0,1,2,3,4,5,6);
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-18916: crash in Window_spec::print_partition() with decimals
+--echo #
+
+--error ER_TOO_BIG_SCALE
+SELECT cast((rank() over w1) as decimal (53,56));
+--error ER_WRONG_WINDOW_SPEC_NAME
+SELECT cast((rank() over w1) as decimal (53,30));
+
 --echo #
 --echo # End of 10.2 tests
 --echo #
diff --git a/sql/item_windowfunc.cc b/sql/item_windowfunc.cc
index a3edacd880ef2..87dddbfb43963 100644
--- a/sql/item_windowfunc.cc
+++ b/sql/item_windowfunc.cc
@@ -443,10 +443,8 @@ void Item_window_func::print(String *str, enum_query_type query_type)
 {
   window_func()->print(str, query_type);
   str->append(" over ");
-#ifndef DBUG_OFF
-  if (!window_spec) // one can call dbug_print_item() anytime in gdb
+  if (!window_spec)
     str->append(window_name);
   else
-#endif
-  window_spec->print(str, query_type);
+    window_spec->print(str, query_type);
 }