diff --git a/dlib/svm/svm_c_linear_trainer.h b/dlib/svm/svm_c_linear_trainer.h
index a546ffc0f..81c0078eb 100644
--- a/dlib/svm/svm_c_linear_trainer.h
+++ b/dlib/svm/svm_c_linear_trainer.h
@@ -315,7 +315,7 @@ namespace dlib
         const in_scalar_vector_type& labels,
         const bool be_verbose,
         const scalar_type eps,
-        const unsigned char max_iterations
+        const unsigned long max_iterations
     )
     {
         return oca_problem_c_svm<matrix_type, in_sample_vector_type, in_scalar_vector_type>(