diff --git a/rhizome_fetch.c b/rhizome_fetch.c
index 486746fc..6e63b78f 100644
--- a/rhizome_fetch.c
+++ b/rhizome_fetch.c
@@ -57,9 +57,13 @@ struct rhizome_fetch_slot {
 #define RHIZOME_FETCH_RXHTTPHEADERS 3
 #define RHIZOME_FETCH_RXFILE 4
 #define RHIZOME_FETCH_RXFILEMDP 5
+
+  /* Keep track of how much of the file we have read */
+  SHA512_CTX sha512_context;
   int64_t rowid;
   int64_t file_len;
   int64_t file_ofs;
+
   int64_t last_write_time;
 
   /* HTTP transport specific elements */
@@ -509,6 +513,7 @@ static int schedule_fetch(struct rhizome_fetch_slot *slot)
 		alloca_tohex_sid(slot->bid));
     goto bail;
   }
+  SHA512_Init(&slot->sha512_context);
   if (slot->peer_ipandport.sin_family == AF_INET) {
     /* Transfer via HTTP over IPv4 */
     if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
@@ -1195,6 +1200,8 @@ void rhizome_fetch_write(struct rhizome_fetch_slot *slot)
 
 int rhizome_write_content(struct rhizome_fetch_slot *slot, char *buffer, int bytes)
 {
+  // Truncate to known length of file (handy for reading from journal bundles that
+  // might grow while we are reading from them).
   if (bytes>(slot->file_len-slot->file_ofs))
     bytes=slot->file_len-slot->file_ofs;
   
@@ -1216,8 +1223,10 @@ int rhizome_write_content(struct rhizome_fetch_slot *slot, char *buffer, int byt
       rhizome_fetch_close(slot);
       return -1;
     }
-    DEBUGF("XXX - Do progressive hash of content here");
-    return -1;
+
+    SHA512_Update(&slot->sha512_context,(unsigned char *)buffer,bytes);
+
+    sqlite3_blob_close(blob); blob=NULL;
   }
 
   slot->file_ofs+=bytes;
@@ -1228,6 +1237,27 @@ int rhizome_write_content(struct rhizome_fetch_slot *slot, char *buffer, int byt
       DEBUGF("Received all of file via rhizome -- now to import it");
     if (slot->manifest) {
       // Were fetching payload, now we have it.
+
+      char hash_out[SHA512_DIGEST_STRING_LENGTH+1];
+      SHA512_End(&slot->sha512_context, (char *)hash_out);
+      
+      DEBUGF("Hash of received file = %s",hash_out);
+      DEBUGF("Hash I was looking for = %s",slot->manifest->fileHexHash);
+
+      sqlite_retry_state retry = SQLITE_RETRY_STATE_DEFAULT;
+      if (strcasecmp(hash_out,slot->manifest->fileHexHash)) {
+	DEBUGF("Hash mismatch -- dropping row from table.");	
+	sqlite_exec_void_retry(&retry,
+			       "DROP FROM FILES WHERE rowid=%lld",slot->rowid);
+	rhizome_fetch_close(slot);
+	return -1;
+      } else {
+	sqlite_exec_void_retry(&retry,
+			       "UPDATE FILES SET datavalid=1 WHERE rowid=%lld",
+				slot->rowid);
+	DEBUGF("Marked row valid");
+      }
+
       if (!rhizome_import_received_bundle(slot->manifest)){
 	if (slot->state==RHIZOME_FETCH_RXFILE) {
 	  char buf[INET_ADDRSTRLEN];