diff --git a/examples/mnist/mnist-common.cpp b/examples/mnist/mnist-common.cpp
index 87666c02b..f0e90bb02 100644
--- a/examples/mnist/mnist-common.cpp
+++ b/examples/mnist/mnist-common.cpp
@@ -74,8 +74,8 @@ mnist_eval_result mnist_graph_eval(const std::string & fname, const float * imag
     fprintf(stderr, "%s: trying to load a ggml graph from %s\n", __func__, fname.c_str());
     mnist_eval_result result;
 
-    struct ggml_context * ctx_data = NULL;
-    struct ggml_context * ctx_eval = NULL;
+    struct ggml_context * ctx_data = nullptr;
+    struct ggml_context * ctx_eval = nullptr;
 
     struct ggml_cgraph * gf;
     {