diff --git a/src/finn/custom_op/fpgadataflow/__init__.py b/src/finn/custom_op/fpgadataflow/__init__.py
index 9d41df33e68f719c6a158f9ff59e2ea45392741a..a688898f4a43b33fd3f07cda12144b84829e451f 100644
--- a/src/finn/custom_op/fpgadataflow/__init__.py
+++ b/src/finn/custom_op/fpgadataflow/__init__.py
@@ -217,6 +217,8 @@ class HLSCustomOp(CustomOp):
         self.code_gen_dict["$FINNHLSLIBDIR$"] = ["/workspace/finn-hlslib"]
         self.code_gen_dict["$TOPFXN$"] = [node.name]
         self.code_gen_dict["$CLKPERIOD$"] = [str(clk)]
+        self.code_gen_dict["$EXTRA_DIRECTIVES$"] = self.ipgen_extra_directives()
+
 
         template = self.ipgentcl_template
 
@@ -230,6 +232,10 @@ class HLSCustomOp(CustomOp):
         f.close()
         self.code_gen_dict.clear()
 
+    def ipgen_extra_directives(self):
+        "Return a list of extra tcl directives for HLS synthesis."
+        return []
+        
     def ipgen_singlenode_code(self):
         """Builds the bash script for ip generation using the IPGenBuilder from
         finn.util.fpgadataflow."""