diff --git a/include/errmsg.h b/include/errmsg.h
index 4afe8e8a..0d8ddcaf 100644
--- a/include/errmsg.h
+++ b/include/errmsg.h
@@ -114,10 +114,11 @@ extern const char *mariadb_client_errors[];	/* Error messages */
 #define CR_BINLOG_ERROR 5021
 #define CR_BINLOG_INVALID_FILE 5022
 #define CR_BINLOG_SEMI_SYNC_ERROR 5023
+#define CR_STMT_NO_RESULT 5024
 
 /* Always last, if you add new error codes please update the
    value for CR_MARIADB_LAST_ERROR */
-#define CR_MARIADB_LAST_ERROR CR_BINLOG_INVALID_FILE
+#define CR_MARIADB_LAST_ERROR CR_STMT_NO_RESULT
 
 #endif
 
diff --git a/libmariadb/ma_errmsg.c b/libmariadb/ma_errmsg.c
index 1f3fa408..1fcc6d4a 100644
--- a/libmariadb/ma_errmsg.c
+++ b/libmariadb/ma_errmsg.c
@@ -118,6 +118,7 @@ const char *mariadb_client_errors[] =
   /* 5021 */ "Binary log error (File: %.*s start_pos=%ld): %s.",
   /* 5022 */ "File '%s' is not a binary log file",
   /* 5023 */ "Semi sync request error: %s",
+  /* 5024 */ "Statement has no result set",
   ""
 };
 
diff --git a/libmariadb/mariadb_stmt.c b/libmariadb/mariadb_stmt.c
index 1a20bcca..92f1869c 100644
--- a/libmariadb/mariadb_stmt.c
+++ b/libmariadb/mariadb_stmt.c
@@ -1613,6 +1613,12 @@ unsigned int STDCALL mysql_stmt_field_count(MYSQL_STMT *stmt)
 
 my_bool STDCALL mysql_stmt_free_result(MYSQL_STMT *stmt)
 {
+  if (stmt->state < MYSQL_STMT_EXECUTED || !stmt->field_count)
+  {
+    stmt_set_error(stmt, CR_STMT_NO_RESULT, SQLSTATE_UNKNOWN, 0);
+    return 1;
+  }
+
   return madb_reset_stmt(stmt, MADB_RESET_LONGDATA | MADB_RESET_STORED |
                                MADB_RESET_BUFFER | MADB_RESET_ERROR);
 }
@@ -2198,6 +2204,19 @@ static my_bool madb_reset_stmt(MYSQL_STMT *stmt, unsigned int flags)
 {
   MYSQL *mysql= stmt->mysql;
   my_bool ret= 0;
+  LIST *li_stmt= mysql->stmts;
+
+  /* CONC-667: If an other statement has a pending result set, we
+     need to return an error */
+  for (;li_stmt;li_stmt= li_stmt->next)
+  {
+    MYSQL_STMT *s= (MYSQL_STMT *)li_stmt->data;
+    if (s != stmt && s->state == MYSQL_STMT_WAITING_USE_OR_STORE)
+    {
+      stmt_set_error(stmt, CR_COMMANDS_OUT_OF_SYNC, SQLSTATE_UNKNOWN, 0);
+      return 1;
+    }
+  }
 
   if (!stmt->mysql)
   {
@@ -2297,7 +2316,8 @@ static my_bool mysql_stmt_internal_reset(MYSQL_STMT *stmt, my_bool is_close)
       stmt->fetch_row_func == stmt_unbuffered_fetch)
     flags|= MADB_RESET_BUFFER;
 
-  ret= madb_reset_stmt(stmt, flags);
+  if (ret= madb_reset_stmt(stmt, flags))
+    return ret;
 
   if (stmt->stmt_id)
   {
diff --git a/unittest/libmariadb/ps_bugs.c b/unittest/libmariadb/ps_bugs.c
index 804ef3e3..562ea3ff 100644
--- a/unittest/libmariadb/ps_bugs.c
+++ b/unittest/libmariadb/ps_bugs.c
@@ -5741,7 +5741,47 @@ end:
   return ret;
 }
 
+static int test_conc667(MYSQL *mysql)
+{
+  MYSQL_STMT *stmt1, *stmt2;
+  int rc;
+
+  stmt1= mysql_stmt_init(mysql);
+  stmt2= mysql_stmt_init(mysql);
+
+  rc= mysql_stmt_prepare(stmt1, "SELECT 1", -1);
+  check_stmt_rc(rc, stmt1);
+
+  rc= mysql_stmt_prepare(stmt2, "SELECT 2", -1);
+  check_stmt_rc(rc, stmt2);
+
+  rc= mysql_stmt_execute(stmt1);
+  check_stmt_rc(rc, stmt1);
+
+  rc= mysql_stmt_free_result(stmt2);
+  FAIL_IF(!rc || mysql_stmt_errno(stmt2) != CR_STMT_NO_RESULT,
+           "Expected CR_STMT_NO_RESULT");
+  diag("Error (expected) %s", mysql_stmt_error(stmt2));
+
+  rc= mysql_stmt_reset(stmt2);
+  FAIL_IF(!rc || mysql_stmt_errno(stmt2) != CR_COMMANDS_OUT_OF_SYNC,
+           "Expected commands out of sync error");
+
+  rc= mysql_stmt_fetch(stmt1);
+  check_stmt_rc(rc, stmt1);
+
+  mysql_stmt_free_result(stmt1);
+
+  rc= mysql_stmt_close(stmt1);
+  check_stmt_rc(rc, stmt1);
+  rc= mysql_stmt_close(stmt2);
+  check_stmt_rc(rc, stmt2);
+
+  return OK;
+}
+
 struct my_tests_st my_tests[] = {
+  {"test_conc667", test_conc667, TEST_CONNECTION_DEFAULT, 0, NULL, NULL},
   {"test_conc633", test_conc633, TEST_CONNECTION_DEFAULT, 0, NULL, NULL},
   {"test_conc623", test_conc623, TEST_CONNECTION_DEFAULT, 0, NULL, NULL},
   {"test_conc627", test_conc627, TEST_CONNECTION_DEFAULT, 0, NULL, NULL},