diff --git a/include/mbedtls/hmac_drbg.h b/include/mbedtls/hmac_drbg.h
index a46b287..2e4e23b 100644
--- a/include/mbedtls/hmac_drbg.h
+++ b/include/mbedtls/hmac_drbg.h
@@ -139,13 +139,11 @@
  *                      Note that SHA-256 is just as efficient as SHA-224.
  *                      The security strength can be reduced if a smaller
  *                      entropy length is set with
- *                      mbedtls_hmac_drbg_set_entropy_len() afterwards.
+ *                      mbedtls_hmac_drbg_set_entropy_len().
  *
- * \note                The entropy length for the initial seeding is
- *                      the security strength (converted from bits to bytes).
- *                      You can set a different entropy length for subsequent
- *                      seeding by calling mbedtls_hmac_drbg_set_entropy_len()
- *                      after this function.
+ * \note                The default entropy length is the security strength
+ *                      (converted from bits to bytes). You can override
+ *                      it by calling mbedtls_hmac_drbg_set_entropy_len().
  *
  * \note                During the initial seeding, this function calls
  *                      the entropy source to obtain a nonce
@@ -224,14 +222,9 @@
 
 /**
  * \brief               This function sets the amount of entropy grabbed on each
- *                      reseed.
+ *                      seed or reseed.
  *
- * The default value is set by mbedtls_hmac_drbg_seed().
- *
- * \note                mbedtls_hmac_drbg_seed() always sets the entropy length
- *                      to the default value based on the chosen MD algorithm,
- *                      so this function only has an effect if it is called
- *                      after mbedtls_hmac_drbg_seed().
+ * See the documentation of mbedtls_hmac_drbg_seed() for the default value.
  *
  * \param ctx           The HMAC_DRBG context.
  * \param len           The amount of entropy to grab, in bytes.
diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c
index 886f44a..346c263 100644
--- a/library/hmac_drbg.c
+++ b/library/hmac_drbg.c
@@ -275,16 +275,19 @@
 
     ctx->reseed_interval = MBEDTLS_HMAC_DRBG_RESEED_INTERVAL;
 
-    /*
-     * See SP800-57 5.6.1 (p. 65-66) for the security strength provided by
-     * each hash function, then according to SP800-90A rev1 10.1 table 2,
-     * min_entropy_len (in bits) is security_strength.
-     *
-     * (This also matches the sizes used in the NIST test vectors.)
-     */
-    ctx->entropy_len = md_size <= 20 ? 16 : /* 160-bits hash -> 128 bits */
-                       md_size <= 28 ? 24 : /* 224-bits hash -> 192 bits */
-                       32;  /* better (256+) -> 256 bits */
+    if( ctx->entropy_len == 0 )
+    {
+        /*
+         * See SP800-57 5.6.1 (p. 65-66) for the security strength provided by
+         * each hash function, then according to SP800-90A rev1 10.1 table 2,
+         * min_entropy_len (in bits) is security_strength.
+         *
+         * (This also matches the sizes used in the NIST test vectors.)
+         */
+        ctx->entropy_len = md_size <= 20 ? 16 : /* 160-bits hash -> 128 bits */
+                           md_size <= 28 ? 24 : /* 224-bits hash -> 192 bits */
+                           32;  /* better (256+) -> 256 bits */
+    }
 
     if( ( ret = hmac_drbg_reseed_core( ctx, custom, len,
                                        1 /* add nonce */ ) ) != 0 )
@@ -305,7 +308,7 @@
 }
 
 /*
- * Set entropy length grabbed for reseeds
+ * Set entropy length grabbed for seeding
  */
 void mbedtls_hmac_drbg_set_entropy_len( mbedtls_hmac_drbg_context *ctx, size_t len )
 {