diff --git a/ChangeLog.d/mpi_fill_random-rng_failure.txt b/ChangeLog.d/mpi_fill_random-rng_failure.txt
new file mode 100644
index 0000000..8addf18
--- /dev/null
+++ b/ChangeLog.d/mpi_fill_random-rng_failure.txt
@@ -0,0 +1,8 @@
+Security
+   * A failure of the random generator was ignored in mbedtls_mpi_fill_random(),
+     which is how most uses of randomization in asymmetric cryptography
+     (including key generation, intermediate value randomization and blinding)
+     are implemented. This could cause failures or the silent use of non-random
+     values. A random generator can fail if it needs reseeding and cannot not
+     obtain entropy, or due to an internal failure (which, for Mbed TLS's own
+     CTR_DRBG or HMAC_DRBG, can only happen due to a misconfiguration).
diff --git a/library/bignum.c b/library/bignum.c
index dfe976d..0d363e6 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -2334,7 +2334,7 @@
     MBEDTLS_MPI_CHK( mbedtls_mpi_lset( X, 0 ) );
 
     Xp = (unsigned char*) X->p;
-    f_rng( p_rng, Xp + overhead, size );
+    MBEDTLS_MPI_CHK( f_rng( p_rng, Xp + overhead, size ) );
 
     mpi_bigendian_to_host( X->p, limbs );