diff --git a/library/psa_util.c b/library/psa_util.c
index 679d00e..014e648 100644
--- a/library/psa_util.c
+++ b/library/psa_util.c
@@ -440,6 +440,9 @@
     unsigned char *p = der + der_size;
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
+    if (bits == 0) {
+        return MBEDTLS_ERR_ASN1_INVALID_DATA;
+    }
     if (raw_len != (2 * coordinate_len)) {
         return MBEDTLS_ERR_ASN1_INVALID_DATA;
     }
@@ -559,6 +562,9 @@
     size_t coordinate_size = PSA_BITS_TO_BYTES(bits);
     int ret;
 
+    if (bits == 0) {
+        return MBEDTLS_ERR_ASN1_INVALID_DATA;
+    }
     /* The output raw buffer should be at least twice the size of a raw
      * coordinate in order to store r and s. */
     if (raw_size < coordinate_size * 2) {