diff --git a/mysql-test/main/create.result b/mysql-test/main/create.result
index 4bae81878103b..d901ead20f613 100644
--- a/mysql-test/main/create.result
+++ b/mysql-test/main/create.result
@@ -2066,3 +2066,9 @@ SHOW CREATE DATABASE `#testone#￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
 ERROR 42000: Incorrect database name '#testone#￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭...'
 SET NAMES DEFAULT;
 # End of 10.5 Test
+#
+# MDEV-39002: Diagnostics area assertion failure upon CREATE TABLE
+#
+CREATE TABLE t1 (a INT, b VARCHAR(8) DEFAULT (IFNULL(a,''))) CHARSET swe7;
+ERROR HY000: Illegal mix of collations (latin1_swedish_ci,NUMERIC) and (swe7_swedish_ci,COERCIBLE) for operation 'ifnull'
+End of 10.11 tests
diff --git a/mysql-test/main/create.test b/mysql-test/main/create.test
index dada6963fdb2e..74c100b5ee601 100644
--- a/mysql-test/main/create.test
+++ b/mysql-test/main/create.test
@@ -1945,3 +1945,12 @@ SHOW CREATE DATABASE `#testone#￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
 SET NAMES DEFAULT;
 
 --echo # End of 10.5 Test
+
+--echo #
+--echo # MDEV-39002: Diagnostics area assertion failure upon CREATE TABLE
+--echo #
+
+--error ER_CANT_AGGREGATE_2COLLATIONS
+CREATE TABLE t1 (a INT, b VARCHAR(8) DEFAULT (IFNULL(a,''))) CHARSET swe7;
+
+--echo End of 10.11 tests
diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index 753d939f6560d..d47394818faec 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -1207,9 +1207,9 @@ class Item_func_coalesce :public Item_func_case_expression
   bool fix_length_and_dec(THD *thd) override
   {
     update_nullability_post_fix_fields();
-    if (aggregate_for_result(func_name_cstring(), args, arg_count, true))
+    if (aggregate_for_result(func_name_cstring(), args, arg_count, true) ||
+        fix_attributes(args, arg_count))
       return TRUE;
-    fix_attributes(args, arg_count);
     return FALSE;
   }
   LEX_CSTRING func_name_cstring() const override
@@ -1236,9 +1236,9 @@ class Item_func_case_abbreviation2 :public Item_func_case_expression
 protected:
   bool fix_length_and_dec2(Item **items)
   {
-    if (aggregate_for_result(func_name_cstring(), items, 2, true))
+    if (aggregate_for_result(func_name_cstring(), items, 2, true) ||
+        fix_attributes(items, 2))
       return TRUE;
-    fix_attributes(items, 2);
     return FALSE;
   }