diff --git a/modules/dnn/src/onnx/onnx_graph_simplifier.cpp b/modules/dnn/src/onnx/onnx_graph_simplifier.cpp
index 10c4161cfe..e27be30cd3 100644
--- a/modules/dnn/src/onnx/onnx_graph_simplifier.cpp
+++ b/modules/dnn/src/onnx/onnx_graph_simplifier.cpp
@@ -98,7 +98,7 @@ private:
 class SoftMaxSubgraph : public Subgraph
 {
 public:
-    SoftMaxSubgraph()
+    SoftMaxSubgraph() : axis(1)
     {
         int input = addNodeToMatch("");
         int inpExp = addNodeToMatch("Exp", input);