diff --git a/src/apps/snmp/snmp_msg.c b/src/apps/snmp/snmp_msg.c
index 7d6eefd1..faa5a5b4 100644
--- a/src/apps/snmp/snmp_msg.c
+++ b/src/apps/snmp/snmp_msg.c
@@ -1672,7 +1672,7 @@ snmp_complete_outbound_frame(struct snmp_request *request)
     struct snmp_pbuf_stream inbound_stream;
     OF_BUILD_EXEC( snmp_pbuf_stream_init(&inbound_stream, request->inbound_pbuf, request->inbound_varbind_offset, request->inbound_varbind_len) );
     OF_BUILD_EXEC( snmp_pbuf_stream_init(&(request->outbound_pbuf_stream), request->outbound_pbuf, request->outbound_varbind_offset, request->outbound_pbuf->tot_len - request->outbound_varbind_offset) );
-    snmp_pbuf_stream_writeto(&inbound_stream, &(request->outbound_pbuf_stream), 0);
+    OF_BUILD_EXEC( snmp_pbuf_stream_writeto(&inbound_stream, &(request->outbound_pbuf_stream), 0) );
   }
 
   frame_size = request->outbound_pbuf_stream.offset;
@@ -1683,7 +1683,7 @@ snmp_complete_outbound_frame(struct snmp_request *request)
     u8_t i;
     outbound_padding = (8 - (u8_t)((frame_size - request->outbound_scoped_pdu_seq_offset) & 0x07)) & 0x07;
     for (i = 0; i < outbound_padding; i++) {
-      snmp_pbuf_stream_write(&request->outbound_pbuf_stream, 0);
+      OF_BUILD_EXEC( snmp_pbuf_stream_write(&request->outbound_pbuf_stream, 0) );
     }
   }
 #endif
diff --git a/src/apps/snmp/snmpv3_mbedtls.c b/src/apps/snmp/snmpv3_mbedtls.c
index b90badf5..ec4ba38b 100644
--- a/src/apps/snmp/snmpv3_mbedtls.c
+++ b/src/apps/snmp/snmpv3_mbedtls.c
@@ -154,29 +154,36 @@ snmpv3_crypt(struct snmp_pbuf_stream* stream, u16_t length,
       out_len = LWIP_ARRAYSIZE(out_bytes) ;
       
       for (j = 0; j < LWIP_ARRAYSIZE(in_bytes); j++) {
-        snmp_pbuf_stream_read(&read_stream, &in_bytes[j]);
+        if (snmp_pbuf_stream_read(&read_stream, &in_bytes[j]) != ERR_OK) {
+          goto error;
+        }
       }
 
-      if(mbedtls_cipher_update(&ctx, in_bytes, LWIP_ARRAYSIZE(in_bytes), out_bytes, &out_len) != 0) {
+      if (mbedtls_cipher_update(&ctx, in_bytes, LWIP_ARRAYSIZE(in_bytes), out_bytes, &out_len) != 0) {
         goto error;
       }
 
-      snmp_pbuf_stream_writebuf(&write_stream, out_bytes, (u16_t)out_len);
+      if (snmp_pbuf_stream_writebuf(&write_stream, out_bytes, (u16_t)out_len) != ERR_OK) {
+        goto error;
+      }
     }
     
     out_len = LWIP_ARRAYSIZE(out_bytes);
-    if(mbedtls_cipher_finish(&ctx, out_bytes, &out_len) != 0) {
+    if (mbedtls_cipher_finish(&ctx, out_bytes, &out_len) != 0) {
+      goto error;
+    }
+    
+    if (snmp_pbuf_stream_writebuf(&write_stream, out_bytes, (u16_t)out_len) != ERR_OK) {
       goto error;
     }
-    snmp_pbuf_stream_writebuf(&write_stream, out_bytes, (u16_t)out_len);
   } else if (algo == SNMP_V3_PRIV_ALGO_AES) {
     u8_t iv_local[16];
 
     cipher_info = mbedtls_cipher_info_from_type(MBEDTLS_CIPHER_AES_128_CFB128);
-    if(mbedtls_cipher_setup(&ctx, cipher_info) != 0) {
+    if (mbedtls_cipher_setup(&ctx, cipher_info) != 0) {
       return ERR_ARG;
     }
-    if(mbedtls_cipher_setkey(&ctx, key, 16*8, (mode == SNMP_V3_PRIV_MODE_ENCRYPT)? MBEDTLS_ENCRYPT : MBEDTLS_DECRYPT) != 0) {
+    if (mbedtls_cipher_setkey(&ctx, key, 16*8, (mode == SNMP_V3_PRIV_MODE_ENCRYPT)? MBEDTLS_ENCRYPT : MBEDTLS_DECRYPT) != 0) {
       goto error;
     }
 
@@ -202,11 +209,15 @@ snmpv3_crypt(struct snmp_pbuf_stream* stream, u16_t length,
       u8_t out_byte;
       size_t out_len = sizeof(out_byte);
       
-      snmp_pbuf_stream_read(&read_stream, &in_byte);
-      if(mbedtls_cipher_update(&ctx, &in_byte, sizeof(in_byte), &out_byte, &out_len) != 0) {
+      if (snmp_pbuf_stream_read(&read_stream, &in_byte) != ERR_OK) {
+        goto error;
+      }
+      if (mbedtls_cipher_update(&ctx, &in_byte, sizeof(in_byte), &out_byte, &out_len) != 0) {
+        goto error;
+      }
+      if (snmp_pbuf_stream_write(&write_stream, out_byte) != ERR_OK) {
         goto error;
       }
-      snmp_pbuf_stream_write(&write_stream, out_byte);
     }
   } else {
     return ERR_ARG;