diff --git a/ChangeLog.d/fix-a-few-unchecked-return.txt b/ChangeLog.d/fix-a-few-unchecked-return.txt
new file mode 100644
index 000000000..aadde3631
--- /dev/null
+++ b/ChangeLog.d/fix-a-few-unchecked-return.txt
@@ -0,0 +1,3 @@
+Bugfix
+   * Fix some cases where mbedtls_mpi_mod_exp, RSA key construction or ECDSA
+     signature can silently return an incorrect result in low memory conditions.
diff --git a/library/bignum.c b/library/bignum.c
index b1518ede0..f6bdf7edb 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -2033,7 +2033,7 @@ int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A,
     /*
      * Load the result in the output variable.
      */
-    mbedtls_mpi_copy(X, &W[x_index]);
+    MBEDTLS_MPI_CHK(mbedtls_mpi_copy(X, &W[x_index]));
 
 cleanup:
 
diff --git a/library/ecdsa.c b/library/ecdsa.c
index 1faec1639..6e55f2205 100644
--- a/library/ecdsa.c
+++ b/library/ecdsa.c
@@ -373,7 +373,7 @@ modn:
 
 #if defined(MBEDTLS_ECP_RESTARTABLE)
     if (rs_ctx != NULL && rs_ctx->sig != NULL) {
-        mbedtls_mpi_copy(r, pr);
+        MBEDTLS_MPI_CHK(mbedtls_mpi_copy(r, pr));
     }
 #endif
 
@@ -447,7 +447,7 @@ int mbedtls_ecdsa_sign_det_restartable(mbedtls_ecp_group *grp,
     MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(d, data, grp_len));
     MBEDTLS_MPI_CHK(derive_mpi(grp, &h, buf, blen));
     MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&h, data + grp_len, grp_len));
-    mbedtls_hmac_drbg_seed_buf(p_rng, md_info, data, 2 * grp_len);
+    MBEDTLS_MPI_CHK(mbedtls_hmac_drbg_seed_buf(p_rng, md_info, data, 2 * grp_len));
 
 #if defined(MBEDTLS_ECP_RESTARTABLE)
     if (rs_ctx != NULL && rs_ctx->det != NULL) {
diff --git a/library/rsa_alt_helpers.c b/library/rsa_alt_helpers.c
index 3451469b9..5cc4636e4 100644
--- a/library/rsa_alt_helpers.c
+++ b/library/rsa_alt_helpers.c
@@ -126,7 +126,7 @@ int mbedtls_rsa_deduce_primes(mbedtls_mpi const *N,
     }
 
     for (; attempt < num_primes; ++attempt) {
-        mbedtls_mpi_lset(&K, primes[attempt]);
+        MBEDTLS_MPI_CHK(mbedtls_mpi_lset(&K, primes[attempt]));
 
         /* Check if gcd(K,N) = 1 */
         MBEDTLS_MPI_CHK(mbedtls_mpi_gcd(P, &K, N));