diff --git a/tests/bugs/gh_7590_test.py b/tests/bugs/gh_7590_test.py
new file mode 100644
index 00000000..5625eec7
--- /dev/null
+++ b/tests/bugs/gh_7590_test.py
@@ -0,0 +1,79 @@
+#coding:utf-8
+
+"""
+ID:          issue-7590
+ISSUE:       https://github.com/FirebirdSQL/firebird/issues/7590
+TITLE:       Improve DECLARE VARIABLE to accept complete value expressions
+DESCRIPTION:
+    Test only ckecks ability to use feature as it is described in the doc.
+    More complex tests will be implemented later.
+NOTES:
+    [02.10.2023] pzotov
+    Checked on 6.0.0.65.
+"""
+
+import pytest
+from firebird.qa import *
+
+db = db_factory()
+
+test_script = """
+    set list on;
+    set term ^;
+    execute block returns (o1 integer, o2 integer) as
+
+        declare function sf1 returns integer;
+        declare v0 integer = sf1();
+        declare v1 integer;
+        declare v2 integer = 2;
+
+        declare function sf1 returns integer
+        as
+        begin
+            v1 = 10;
+            v2 = 20;
+            return 0;
+        end
+    begin
+        o1 = v1;
+        o2 = v2;
+        suspend;
+    end
+    ^
+
+    -- It's an error if a subroutine reads a variable declared after the one being initialized like in the following example.
+    -- When sf1 is called, v1 is not yet initialized.
+    execute block returns(msg varchar(20)) as
+        declare function sf1 returns integer;
+
+        declare v0 integer = sf1();
+        declare v1 integer;
+
+        declare function sf1 returns integer
+        as
+        begin
+            return v1;
+        end
+    begin
+        msg = 'UNEXPECTEDLY successful execution.';
+        suspend;
+    end
+    ^
+"""
+substitutions = [ ('[ \t]+', ' '), ('[-]?At\\s+.* line: \\d+, col: \\d+' , 'At line/col') ]
+act = isql_act('db', test_script, substitutions = substitutions)
+
+expected_stdout = """
+    O1 <null>
+    O2 2
+    Statement failed, SQLSTATE = 42000
+    Variable [number 2] is not initialized
+    -At sub function 'SF1' line: 10, col: 13
+    At block line: 5, col: 27
+"""
+
+@pytest.mark.version('>=6.0')
+def test_1(act: Action):
+    act.expected_stdout = expected_stdout
+    act.execute(combine_output = True)
+    assert act.clean_stdout == act.clean_expected_stdout