diff --git a/.changes/next-release/minor-20191004132521.json b/.changes/next-release/minor-20191004132521.json
new file mode 100644
index 00000000..b044df30
--- /dev/null
+++ b/.changes/next-release/minor-20191004132521.json
@@ -0,0 +1,4 @@
+{
+  "type": "minor",
+  "description": "Use the last irreversible block for tapos ref params"
+}
diff --git a/graphenebase/transactions.py b/graphenebase/transactions.py
index f040ec9b..6adeaba8 100644
--- a/graphenebase/transactions.py
+++ b/graphenebase/transactions.py
@@ -16,17 +16,15 @@
 timeformat = "%Y-%m-%dT%H:%M:%S%Z"
 
 
-def getBlockParams(ws):
+def getBlockParams(ws, use_head_block=False):
     """ Auxiliary method to obtain ``ref_block_num`` and
         ``ref_block_prefix``. Requires a websocket connection to a
         witness node!
     """
-    dynBCParams = ws.get_dynamic_global_properties()
-    ref_block_num = dynBCParams["head_block_number"] & 0xFFFF
-    ref_block_prefix = struct.unpack_from(
-        "<I", unhexlify(dynBCParams["head_block_id"]), 4
-    )[0]
-    return ref_block_num, ref_block_prefix
+    raise DeprecationWarning(
+        "This method shouldn't be called anymore. It is part of "
+        "transactionbuilder now"
+    )
 
 
 def formatTimeFromNow(secs=0):
diff --git a/graphenecommon/transactionbuilder.py b/graphenecommon/transactionbuilder.py
index 2578e4b0..f77dc17d 100644
--- a/graphenecommon/transactionbuilder.py
+++ b/graphenecommon/transactionbuilder.py
@@ -405,17 +405,25 @@ def constructTx(self):
         dict.update(self, self.tx.json())
         self._unset_require_reconstruction()
 
-    def get_block_params(self):
+    def get_block_params(self, use_head_block=False):
         """ Auxiliary method to obtain ``ref_block_num`` and
             ``ref_block_prefix``. Requires a websocket connection to a
             witness node!
         """
         ws = self.blockchain.rpc
         dynBCParams = ws.get_dynamic_global_properties()
-        ref_block_num = dynBCParams["head_block_number"] & 0xFFFF
-        ref_block_prefix = struct.unpack_from(
-            "<I", unhexlify(dynBCParams["head_block_id"]), 4
-        )[0]
+        if use_head_block:
+            ref_block_num = dynBCParams["head_block_number"] & 0xFFFF
+            ref_block_prefix = struct.unpack_from(
+                "<I", unhexlify(dynBCParams["head_block_id"]), 4
+            )[0]
+        else:
+            # need to get subsequent block because block head doesn't return 'id' - stupid
+            block = ws.get_block_header(int(dynBCParams["last_irreversible_block_num"])+1)
+            ref_block_num = dynBCParams["last_irreversible_block_num"] & 0xFFFF
+            ref_block_prefix = struct.unpack_from(
+                "<I", unhexlify(block["previous"]), 4
+            )[0]
         return ref_block_num, ref_block_prefix
 
     def sign(self):