diff --git a/client/sql_string.cc b/client/sql_string.cc
index 0ad79ba5633..c404cc6b09f 100644
--- a/client/sql_string.cc
+++ b/client/sql_string.cc
@@ -691,7 +691,7 @@ String *copy_if_not_alloced(String *to,String *from,uint32 from_length)
 {
   if (from->Alloced_length >= from_length)
     return from;
-  if (from->alloced || !to || from == to)
+  if ((from->alloced && (from->Alloced_length != 0)) || !to || from == to)
   {
     (void) from->realloc(from_length);
     return from;
diff --git a/sql/sql_string.cc b/sql/sql_string.cc
index fcd134aff04..22059c3a99c 100644
--- a/sql/sql_string.cc
+++ b/sql/sql_string.cc
@@ -732,7 +732,7 @@ String *copy_if_not_alloced(String *to,String *from,uint32 from_length)
 {
   if (from->Alloced_length >= from_length)
     return from;
-  if (from->alloced || !to || from == to)
+  if ((from->alloced && (from->Alloced_length != 0)) || !to || from == to)
   {
     (void) from->realloc(from_length);
     return from;