diff --git a/cpp/include/cuopt/linear_programming/cuopt_c.h b/cpp/include/cuopt/linear_programming/cuopt_c.h
index 4426b640de..7930fee32d 100644
--- a/cpp/include/cuopt/linear_programming/cuopt_c.h
+++ b/cpp/include/cuopt/linear_programming/cuopt_c.h
@@ -959,7 +959,7 @@ cuopt_int_t cuOptGetErrorStatus(cuOptSolution solution, cuopt_int_t* error_statu
  * @param[out] error_string_ptr - A pointer to a char that on output will contain the
  *  error string.
  *
- * @param[in] error_string_size - Size of the char buffer/
+ * @param[in] error_string_size - Size of the char buffer. Must be positive.
  *
  * @return A status code indicating success or failure.
  */
diff --git a/cpp/src/pdlp/cuopt_c.cpp b/cpp/src/pdlp/cuopt_c.cpp
index fa27e4504b..b663e9078a 100644
--- a/cpp/src/pdlp/cuopt_c.cpp
+++ b/cpp/src/pdlp/cuopt_c.cpp
@@ -1174,6 +1174,7 @@ cuopt_int_t cuOptGetErrorString(cuOptSolution solution,
 {
   if (solution == nullptr) { return CUOPT_INVALID_ARGUMENT; }
   if (error_string_ptr == nullptr) { return CUOPT_INVALID_ARGUMENT; }
+  if (error_string_size <= 0) { return CUOPT_INVALID_ARGUMENT; }
   solution_and_stream_view_t* solution_and_stream_view =
     static_cast<solution_and_stream_view_t*>(solution);
   std::string error_string = solution_and_stream_view->get_solution()->get_error_status().what();
diff --git a/cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp b/cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp
index 9a92f7a310..0e33f3494b 100644
--- a/cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp
+++ b/cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp
@@ -14,6 +14,8 @@
 #include <string>
 
 #include <cuopt/linear_programming/cuopt_c.h>
+#include <cuopt/error.hpp>
+#include <cuopt/linear_programming/cpu_optimization_problem_solution.hpp>
 #include <pdlp/cuopt_c_internal.hpp>
 
 #include <utilities/common_utils.hpp>
@@ -107,6 +109,25 @@ TEST(c_api, solve_time_bb_preemption)
 
 TEST(c_api, bad_parameter_name) { EXPECT_EQ(test_bad_parameter_name(), CUOPT_INVALID_ARGUMENT); }
 
+TEST(c_api, get_error_string_rejects_non_positive_buffer_size)
+{
+  using cuopt::linear_programming::cpu_lp_solution_t;
+  using cuopt::linear_programming::memory_backend_t;
+  using cuopt::linear_programming::pdlp_termination_status_t;
+  using cuopt::linear_programming::solution_and_stream_view_t;
+
+  solution_and_stream_view_t solution_handle(false, memory_backend_t::CPU);
+  solution_handle.lp_solution_interface_ptr = new cpu_lp_solution_t<cuopt_int_t, cuopt_float_t>(
+    pdlp_termination_status_t::NumericalError,
+    cuopt::logic_error("validation failed", cuopt::error_type_t::ValidationError));
+
+  char error_string[32] = {};
+  EXPECT_EQ(cuOptGetErrorString(&solution_handle, error_string, 0), CUOPT_INVALID_ARGUMENT);
+  EXPECT_EQ(cuOptGetErrorString(&solution_handle, error_string, -1), CUOPT_INVALID_ARGUMENT);
+  EXPECT_EQ(cuOptGetErrorString(&solution_handle, error_string, sizeof(error_string)),
+            CUOPT_SUCCESS);
+}
+
 TEST(c_api, mip_get_callbacks_only) { EXPECT_EQ(test_mip_get_callbacks_only(), CUOPT_SUCCESS); }
 
 TEST(c_api, mip_get_set_callbacks) { EXPECT_EQ(test_mip_get_set_callbacks(), CUOPT_SUCCESS); }