diff --git a/tests/include/test/bignum_helpers.h b/tests/include/test/bignum_helpers.h
index ab3c86a..164017e 100644
--- a/tests/include/test/bignum_helpers.h
+++ b/tests/include/test/bignum_helpers.h
@@ -61,7 +61,8 @@
  * the length of the input. In other words, it preserves leading zeros.
  *
  * The limb array is allocated with mbedtls_calloc() and must later be
- * freed with mbedtls_free().
+ * freed with mbedtls_free(). You can do that by calling
+ * mbedtls_test_mpi_mod_modulus_free_with_limbs().
  *
  * \param[in,out] N     A modulus structure. It must be initialized, but
  *                      not set up.
@@ -74,6 +75,13 @@
                                    const char *s,
                                    mbedtls_mpi_mod_rep_selector int_rep );
 
+/** Free a modulus and its limbs.
+ *
+ * \param[in] N         A modulus structure such that there is no other
+ *                      reference to `N->p`.
+ */
+void mbedtls_test_mpi_mod_modulus_free_with_limbs( mbedtls_mpi_mod_modulus *N );
+
 /** Read an MPI from a hexadecimal string.
  *
  * Like mbedtls_mpi_read_string(), but with tighter guarantees around
diff --git a/tests/src/bignum_helpers.c b/tests/src/bignum_helpers.c
index eb819f5..d6ec9bd 100644
--- a/tests/src/bignum_helpers.c
+++ b/tests/src/bignum_helpers.c
@@ -102,6 +102,12 @@
     return( ret );
 }
 
+void mbedtls_test_mpi_mod_modulus_free_with_limbs( mbedtls_mpi_mod_modulus *N )
+{
+    mbedtls_free( (mbedtls_mpi_uint*) N->p );
+    mbedtls_mpi_mod_modulus_free( N );
+}
+
 int mbedtls_test_read_mpi( mbedtls_mpi *X, const char *s )
 {
     int negative = 0;
diff --git a/tests/suites/test_suite_bignum_random.function b/tests/suites/test_suite_bignum_random.function
index a837e1b..5064a62 100644
--- a/tests/suites/test_suite_bignum_random.function
+++ b/tests/suites/test_suite_bignum_random.function
@@ -208,7 +208,7 @@
                     &rnd_mod_raw, sizeof( rnd_mod_raw ) );
 
 exit:
-    mbedtls_mpi_mod_modulus_free( &N );
+    mbedtls_test_mpi_mod_modulus_free_with_limbs( &N );
     mbedtls_free( R_core );
     mbedtls_free( R_mod_raw );
 }