diff --git a/c/cobyla_c.f90 b/c/cobyla_c.f90
index e0ac273e01..36db0414e0 100644
--- a/c/cobyla_c.f90
+++ b/c/cobyla_c.f90
@@ -71,6 +71,7 @@ subroutine cobyla_c(m_nlcon, cobjcon_ptr, data_ptr, n, x, f, cstrv, nlconstr, m_
 real(RP) :: beq_loc(m_eq)
 real(RP) :: bineq_loc(m_ineq)
 real(RP) :: cstrv_loc
+real(RP) :: ctol_loc
 real(RP) :: f_loc
 real(RP) :: ftarget_loc
 real(RP) :: nlconstr_loc(m_nlcon)
@@ -79,7 +80,6 @@ subroutine cobyla_c(m_nlcon, cobjcon_ptr, data_ptr, n, x, f, cstrv, nlconstr, m_
 real(RP), allocatable :: nlconstr0_loc(:)
 real(RP), allocatable :: rhobeg_loc
 real(RP), allocatable :: rhoend_loc
-real(RP), allocatable :: ctol_loc
 real(RP), allocatable :: xl_loc(:)
 real(RP), allocatable :: xu_loc(:)
 
@@ -131,9 +131,7 @@ subroutine cobyla_c(m_nlcon, cobjcon_ptr, data_ptr, n, x, f, cstrv, nlconstr, m_
     maxfun_loc = int(maxfun, kind(maxfun_loc))
 end if
 iprint_loc = int(iprint, kind(iprint_loc))
-if (.not. is_nan(ctol)) then
-    ctol_loc = real(ctol, kind(ctol_loc))
-end if
+ctol_loc = real(ctol, kind(ctol_loc))
 
 ! Call the Fortran code
 if (c_associated(callback_ptr)) then
diff --git a/c/include/prima/prima.h b/c/include/prima/prima.h
index 9893108747..6755765729 100644
--- a/c/include/prima/prima.h
+++ b/c/include/prima/prima.h
@@ -73,11 +73,6 @@ typedef enum {
 } prima_rc_t;
 
 
-// Function to get the message string corresponding to a return code
-PRIMAC_API
-const char *prima_get_rc_string(const prima_rc_t rc);
-
-
 /*
  * Objective function required by UOBYQA, NEWUOA, BOBYQA, and LINCOA
  * x     : on input, the vector of variables (should not be modified)
@@ -272,6 +267,9 @@ typedef struct {
     // status: return code
     prima_rc_t status;
 
+    // success: whether the solver returned normally or ran into abnormal conditions
+    bool success;
+
     // message: exit message
     const char *message;
 
@@ -298,10 +296,6 @@ PRIMAC_API
 prima_rc_t prima_minimize(const prima_algorithm_t algorithm, const prima_problem_t problem, const prima_options_t options, prima_result_t *const result);
 
 
-// Function to check if PRIMA returned normally or ran into abnormal conditions
-PRIMAC_API
-bool prima_is_success(const prima_result_t result);
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/c/lincoa_c.f90 b/c/lincoa_c.f90
index cb399bfef2..40864846d4 100644
--- a/c/lincoa_c.f90
+++ b/c/lincoa_c.f90
@@ -68,12 +68,12 @@ subroutine lincoa_c(cobj_ptr, data_ptr, n, x, f, cstrv, m_ineq, Aineq, bineq, m_
 real(RP) :: beq_loc(m_eq)
 real(RP) :: bineq_loc(m_ineq)
 real(RP) :: cstrv_loc
+real(RP) :: ctol_loc
 real(RP) :: f_loc
 real(RP) :: ftarget_loc
 real(RP) :: x_loc(n)
 real(RP), allocatable :: rhobeg_loc
 real(RP), allocatable :: rhoend_loc
-real(RP), allocatable :: ctol_loc
 real(RP), allocatable :: xl_loc(:)
 real(RP), allocatable :: xu_loc(:)
 
@@ -120,9 +120,7 @@ subroutine lincoa_c(cobj_ptr, data_ptr, n, x, f, cstrv, m_ineq, Aineq, bineq, m_
     npt_loc = int(npt, kind(npt_loc))
 end if
 iprint_loc = int(iprint, kind(iprint_loc))
-if (.not. is_nan(ctol)) then
-    ctol_loc = real(ctol, kind(ctol_loc))
-end if
+ctol_loc = real(ctol, kind(ctol_loc))
 
 ! Call the Fortran code
 if (c_associated(callback_ptr)) then
diff --git a/c/prima.c b/c/prima.c
index 5d380971c1..7499216e6c 100644
--- a/c/prima.c
+++ b/c/prima.c
@@ -57,7 +57,7 @@ prima_rc_t prima_init_options(prima_options_t *const options)
     options->rhoend = NAN;  // Will be interpreted by Fortran as not present
     options->iprint = PRIMA_MSG_NONE;
     options->ftarget = -INFINITY;
-    options->ctol = NAN;  // Will be interpreted by Fortran as not present
+    options->ctol = sqrt(DBL_EPSILON);
     return PRIMA_RC_DFT;
 }
 
@@ -263,13 +263,9 @@ prima_rc_t prima_minimize(const prima_algorithm_t algorithm, const prima_problem
     }
 
     result->status = info;
+    result->success = ((result->status == PRIMA_SMALL_TR_RADIUS && result->cstrv <= options.ctol) ||
+                       (result->status == PRIMA_FTARGET_ACHIEVED));
     result->message = prima_get_rc_string(info);
 
     return info;
 }
-
-bool prima_is_success(const prima_result_t result)
-{
-    return (result.status == PRIMA_SMALL_TR_RADIUS ||
-            result.status == PRIMA_FTARGET_ACHIEVED) && (result.cstrv <= sqrt(DBL_EPSILON));
-}
diff --git a/python/_prima.cpp b/python/_prima.cpp
index 98794b453d..f28d90bd71 100644
--- a/python/_prima.cpp
+++ b/python/_prima.cpp
@@ -32,7 +32,7 @@ struct PRIMAResult {
     // Construct PRIMAResult from prima_result_t
     PRIMAResult(const prima_result_t& result, const int num_vars, const int num_constraints, const std::string method)  :
     x(num_vars, result.x),
-    success(prima_is_success(result)),
+    success(result.success),
     status(result.status),
     message(result.message),
     fun(result.f),