diff --git a/PyQt-Plotter-Dialog/parser/expression.py b/PyQt-Plotter-Dialog/parser/expression.py
index ebb59d0..50c579d 100644
--- a/PyQt-Plotter-Dialog/parser/expression.py
+++ b/PyQt-Plotter-Dialog/parser/expression.py
@@ -11,7 +11,7 @@ from .types import FunctionType, OperatorType, ValueType
 class Expression(abc.ABC):
     """
     Abstract base class for a single parsed expression as a tree data
-    structure. It also defines its public function for triggering 
+    structure. It also defines its public function for triggering
     evaluation. Each child class sets `_evaluator` property to a
     function that accepts variables values and produces numpy array.
     """
diff --git a/PyQt-Plotter-Dialog/plotter_dialog/dialog.py b/PyQt-Plotter-Dialog/plotter_dialog/dialog.py
index 29a510b..ac18323 100644
--- a/PyQt-Plotter-Dialog/plotter_dialog/dialog.py
+++ b/PyQt-Plotter-Dialog/plotter_dialog/dialog.py
@@ -16,6 +16,7 @@ import numpy as np
 from .button_group import ButtonGroup
 from .constants import FUNCTION_NAMES
 from .graph_requester import GraphRequester
+from .utils import size
 
 from parser import Parser
 
@@ -189,6 +190,23 @@ class PlotterDialog(QDialog):
                 x = Parser(x_expr).evaluate(self.variable_values)
                 y = Parser(y_expr).evaluate(self.variable_values)
 
+                if size(x) != size(y):
+                    dlg = QMessageBox(
+                        QMessageBox.Critical,
+                        "Ошибка",
+                        "\n\n".join(
+                            (
+                                "Выражения имеют разную размерность",
+                                f'y: "{y}" -> {size(y)}',
+                                f'x: "{x}" -> {size(x)}',
+                            )
+                        ),
+                    )
+                    dlg.exec()
+
+                    graph_requester.LineEditY.setFocus()
+                    return
+
                 xs.append(x)
                 ys.append(y)
                 labels.append(label)
diff --git a/PyQt-Plotter-Dialog/plotter_dialog/utils.py b/PyQt-Plotter-Dialog/plotter_dialog/utils.py
new file mode 100644
index 0000000..07e64bc
--- /dev/null
+++ b/PyQt-Plotter-Dialog/plotter_dialog/utils.py
@@ -0,0 +1,10 @@
+import numpy as np
+
+from parser.types import ValueType
+
+
+def size(x: ValueType) -> int:
+    if isinstance(x, np.ndarray):
+        return x.size
+    else:
+        return 1