diff --git a/include/mbedtls/ccm.h b/include/mbedtls/ccm.h
index 6f991fe..0dc5b59 100644
--- a/include/mbedtls/ccm.h
+++ b/include/mbedtls/ccm.h
@@ -198,6 +198,7 @@
  * \param ctx       The CCM context to use for encryption. This must be
  *                  initialized and bound to a key.
  * \param length    The length of the input data in Bytes.
+ *                  For tag length = 0, input length is ignored.
  * \param iv        The initialization vector (nonce). This must be a readable
  *                  buffer of at least \p iv_len Bytes.
  * \param iv_len    The length of the nonce in Bytes: 7, 8, 9, 10, 11, 12,
@@ -207,6 +208,7 @@
  *                  at least \p ad_len Bytes.
  * \param ad_len    The length of additional data in Bytes.
  *                  This must be less than 2^16 - 2^8.
+ *                  For tag length = 0, AD length can be 0.
  * \param input     The buffer holding the input data. If \p length is greater
  *                  than zero, \p input must be a readable buffer of at least
  *                  that length.
@@ -279,6 +281,7 @@
  * \param ctx       The CCM context to use for decryption. This must be
  *                  initialized and bound to a key.
  * \param length    The length of the input data in Bytes.
+ *                  For tag length = 0, input length is ignored.
  * \param iv        The initialization vector (nonce). This must be a readable
  *                  buffer of at least \p iv_len Bytes.
  * \param iv_len    The length of the nonce in Bytes: 7, 8, 9, 10, 11, 12,
@@ -288,6 +291,7 @@
  *                  at least that \p ad_len Bytes.
  * \param ad_len    The length of additional data in Bytes.
  *                  This must be less than 2^16 - 2^8.
+ *                  For tag length = 0, AD length can be 0.
  * \param input     The buffer holding the input data. If \p length is greater
  *                  than zero, \p input must be a readable buffer of at least
  *                  that length.
diff --git a/library/ccm.c b/library/ccm.c
index 15efff7..e062678 100644
--- a/library/ccm.c
+++ b/library/ccm.c
@@ -150,9 +150,20 @@
     if( !(ctx->state & CCM_STATE__STARTED) || !(ctx->state & CCM_STATE__LENGHTS_SET) )
         return 0;
 
-    if( ctx->tag_len == 0 && \
-        ( ctx->mode == MBEDTLS_CCM_ENCRYPT || ctx->mode == MBEDTLS_CCM_DECRYPT ) )
-        return( MBEDTLS_ERR_CCM_BAD_INPUT );
+    /* CCM expects non-empty tag.
+     * CCM* allows empty tag. For CCM* without tag, ignore plaintext length.
+     */
+    if( ctx->tag_len == 0 )
+    {
+        if( ctx->mode == MBEDTLS_CCM_STAR_ENCRYPT || ctx->mode == MBEDTLS_CCM_STAR_DECRYPT )
+        {
+            ctx->plaintext_len = 0;
+        }
+        else
+        {
+            return( MBEDTLS_ERR_CCM_BAD_INPUT );
+        }
+    }
 
     /*
      * First block:
@@ -342,7 +353,10 @@
         return MBEDTLS_ERR_CCM_BAD_INPUT;
     }
 
-    if( ctx->processed + input_len > ctx->plaintext_len )
+    /* Check against plaintext length only if performing operation with
+     * authentication
+     */
+    if( ctx->tag_len != 0 && ctx->processed + input_len > ctx->plaintext_len )
     {
         return MBEDTLS_ERR_CCM_BAD_INPUT;
     }