diff --git a/osaca/frontend.py b/osaca/frontend.py
index 839d115..135e41b 100644
--- a/osaca/frontend.py
+++ b/osaca/frontend.py
@@ -237,8 +237,8 @@ class Frontend(object):
         if lcd_warning:
             warnings.append("LCDWarning")
 
-        # if INSTR_FLAGS.TP_UNKWN in [flag for instr in kernel for flag in instr.flags]:
-        #    warnings.append("UnknownInstrWarning")
+        if INSTR_FLAGS.TP_UNKWN in [flag for instr in kernel for flag in instr.flags]:
+            warnings.append("UnknownInstrWarning")
 
         tp_sum = ArchSemantics.get_throughput_sum(kernel) or kernel[0].port_pressure
         cp_kernel = kernel_dg.get_critical_path()