diff --git a/flow/designs/asap7/aes-mbff/config.mk b/flow/designs/asap7/aes-mbff/config.mk
index 5536ff6915..1b99d55a65 100644
--- a/flow/designs/asap7/aes-mbff/config.mk
+++ b/flow/designs/asap7/aes-mbff/config.mk
@@ -3,6 +3,9 @@ export PLATFORM               = asap7
 export DESIGN_NAME            = aes_cipher_top
 export DESIGN_NICKNAME        = aes-mbff
 
+# ignore unsynthesizable timing controls
+export SYNTH_SLANG_ARGS += --ignore-timing
+
 export VERILOG_FILES = $(sort $(wildcard $(DESIGN_HOME)/src/aes/*.v))
 export SDC_FILE      = $(DESIGN_HOME)/$(PLATFORM)/aes/constraint.sdc
 
diff --git a/flow/scripts/synth.tcl b/flow/scripts/synth.tcl
index f94b68c60f..7327312e53 100644
--- a/flow/scripts/synth.tcl
+++ b/flow/scripts/synth.tcl
@@ -143,6 +143,11 @@ if {
   synth -flatten -run coarse:fine {*}$synth_full_args
 }
 
+# Resolve internal tristates left by the slang frontend ---
+if { [env_var_equals SYNTH_HDL_FRONTEND slang] } {
+  tribuf -logic
+  opt_clean
+}
 
 if { $::env(SYNTH_MOCK_LARGE_MEMORIES) } {
   memory_collect