diff --git a/bfasst/ninja_flows/flow_utils.py b/bfasst/ninja_flows/flow_utils.py
index 18580b655..d9644da15 100644
--- a/bfasst/ninja_flows/flow_utils.py
+++ b/bfasst/ninja_flows/flow_utils.py
@@ -4,8 +4,6 @@
 
 from bfasst.paths import NINJA_BUILD_PATH
 
-from bfasst.ninja_tools.vivado.synth.vivado_synth import VivadoSynth
-
 
 def get_flows():
     """Get all flows in the flows directory"""
@@ -32,9 +30,3 @@ def create_build_file():
     """Overwrite the build.ninja file when running generation and build steps separately"""
     with open(NINJA_BUILD_PATH, "w") as f:
         f.write("# This file is autogenerated by bfasst\n\n")
-
-
-def configure_vivado_synth_tool(design, flow_args, ooc=False):
-    if isinstance(flow_args, dict) and "synth" in flow_args:
-        return VivadoSynth(design, flow_args["synth"], ooc)
-    return VivadoSynth(design, ooc=ooc)
diff --git a/bfasst/ninja_flows/ninja_flow_manager.py b/bfasst/ninja_flows/ninja_flow_manager.py
index 2d60bc4da..42387f506 100644
--- a/bfasst/ninja_flows/ninja_flow_manager.py
+++ b/bfasst/ninja_flows/ninja_flow_manager.py
@@ -31,6 +31,8 @@ def __init__(self):
 
     def create_flows(self, flow_name, designs, flow_args=None):
         """Create the ninja flows for the given designs."""
+        if flow_args is None:
+            flow_args = {}
         self.flow_name = flow_name
         self.flows = []
         self.designs = []
@@ -101,7 +103,7 @@ def get_design_basenames(designs):
     if parsed_args.flow_args:
         FLOW_ARGS_DICT = json.loads(parsed_args.flow_args.replace("'", '"'))
     else:
-        FLOW_ARGS_DICT = {}
+        FLOW_ARGS_DICT = None
 
     flow_manager = NinjaFlowManager()
     flow_manager.create_flows(
diff --git a/bfasst/ninja_flows/vivado.py b/bfasst/ninja_flows/vivado.py
index 205fc18a2..54787028b 100644
--- a/bfasst/ninja_flows/vivado.py
+++ b/bfasst/ninja_flows/vivado.py
@@ -3,6 +3,7 @@
 from bfasst.ninja_tools.vivado.impl.vivado_impl import VivadoImpl
 from bfasst.paths import NINJA_FLOWS_PATH
 from bfasst.ninja_tools.vivado.synth.vivado_synth import VivadoSynth
+from bfasst.utils.general import ensure
 
 
 class Vivado(Flow):
@@ -11,7 +12,7 @@ class Vivado(Flow):
     def __init__(self, design, flow_args=None, ooc=False):
         super().__init__(design)
         self.ooc = ooc
-        self.vivado_synth_tool = VivadoSynth(design, flow_args.get("synth"), ooc=ooc)
+        self.vivado_synth_tool = VivadoSynth(design, ensure(flow_args, {}).get("synth"), ooc)
         self.vivado_impl_tool = VivadoImpl(design, ooc)
 
     def create_rule_snippets(self):
diff --git a/bfasst/ninja_flows/vivado_bit_analysis.py b/bfasst/ninja_flows/vivado_bit_analysis.py
index d03b2b79d..b7ef02ee0 100644
--- a/bfasst/ninja_flows/vivado_bit_analysis.py
+++ b/bfasst/ninja_flows/vivado_bit_analysis.py
@@ -8,6 +8,7 @@
 from bfasst.ninja_tools.transform.netlist_cleanup import NetlistCleanupTool
 from bfasst.ninja_tools.transform.netlist_phys_to_logical import NetlistPhysToLogicalTool
 from bfasst.ninja_tools.vivado.synth.vivado_synth import VivadoSynth
+from bfasst.utils.general import ensure
 
 
 class VivadoBitAnalysis(Flow):
@@ -15,7 +16,7 @@ class VivadoBitAnalysis(Flow):
 
     def __init__(self, design, flow_args=None):
         super().__init__(design)
-        self.vivado_synth_tool = VivadoSynth(design, flow_args.get("synth"))
+        self.vivado_synth_tool = VivadoSynth(design, ensure(flow_args, {}).get("synth"))
         self.vivado_impl_tool = VivadoImpl(design)
         self.xrev_tool = XrevTool(design)
         self.netlist_cleanup_tool = NetlistCleanupTool(design)
diff --git a/bfasst/ninja_flows/vivado_conformal.py b/bfasst/ninja_flows/vivado_conformal.py
index fbbceae1f..f0e677454 100644
--- a/bfasst/ninja_flows/vivado_conformal.py
+++ b/bfasst/ninja_flows/vivado_conformal.py
@@ -7,6 +7,7 @@
 from bfasst.paths import NINJA_FLOWS_PATH
 from bfasst.types import Vendor
 from bfasst.ninja_tools.vivado.synth.vivado_synth import VivadoSynth
+from bfasst.utils.general import ensure
 
 
 class VivadoConformal(Flow):
@@ -14,7 +15,7 @@ class VivadoConformal(Flow):
 
     def __init__(self, design, flow_args=None):
         super().__init__(design)
-        self.vivado_synth_tool = VivadoSynth(design, flow_args.get("synth"))
+        self.vivado_synth_tool = VivadoSynth(design, ensure(flow_args, {}).get("synth"))
         self.vivado_impl_tool = VivadoImpl(design)
         self.xrev_tool = Xray(design)
         self.conformal_tool = Conformal(design)
diff --git a/bfasst/ninja_flows/vivado_phys_netlist.py b/bfasst/ninja_flows/vivado_phys_netlist.py
index 8967e0487..b18aafaea 100644
--- a/bfasst/ninja_flows/vivado_phys_netlist.py
+++ b/bfasst/ninja_flows/vivado_phys_netlist.py
@@ -5,6 +5,7 @@
 from bfasst.ninja_tools.transform.phys_netlist import PhysNetlist
 from bfasst.paths import NINJA_FLOWS_PATH
 from bfasst.ninja_tools.vivado.synth.vivado_synth import VivadoSynth
+from bfasst.utils.general import ensure
 
 
 class VivadoPhysNetlist(Flow):
@@ -12,7 +13,7 @@ class VivadoPhysNetlist(Flow):
 
     def __init__(self, design, flow_args=None):
         super().__init__(design)
-        self.vivado_synth_tool = VivadoSynth(design, flow_args.get("synth"))
+        self.vivado_synth_tool = VivadoSynth(design, ensure(flow_args, {}).get("synth"))
         self.vivado_impl_tool = VivadoImpl(design)
         self.phys_netlist_tool = PhysNetlist(design)
 
diff --git a/bfasst/ninja_flows/vivado_phys_netlist_cmp.py b/bfasst/ninja_flows/vivado_phys_netlist_cmp.py
index 9e56fe24d..b53bae9ba 100644
--- a/bfasst/ninja_flows/vivado_phys_netlist_cmp.py
+++ b/bfasst/ninja_flows/vivado_phys_netlist_cmp.py
@@ -7,6 +7,7 @@
 from bfasst.ninja_tools.transform.phys_netlist import PhysNetlist
 from bfasst.paths import NINJA_FLOWS_PATH
 from bfasst.ninja_tools.vivado.synth.vivado_synth import VivadoSynth
+from bfasst.utils.general import ensure
 
 
 class VivadoPhysNetlistCmp(Flow):
@@ -14,7 +15,7 @@ class VivadoPhysNetlistCmp(Flow):
 
     def __init__(self, design, flow_args=None):
         super().__init__(design)
-        self.vivado_synth_tool = VivadoSynth(design, flow_args.get("synth"))
+        self.vivado_synth_tool = VivadoSynth(design, ensure(flow_args, {}).get("synth"))
         self.vivado_impl_tool = VivadoImpl(design)
         self.phys_netlist_tool = PhysNetlist(design)
         self.xray_tool = Xray(design)
diff --git a/bfasst/ninja_flows/vivado_phys_netlist_xrev.py b/bfasst/ninja_flows/vivado_phys_netlist_xrev.py
index e5a4e3ce7..fc3403268 100644
--- a/bfasst/ninja_flows/vivado_phys_netlist_xrev.py
+++ b/bfasst/ninja_flows/vivado_phys_netlist_xrev.py
@@ -7,6 +7,7 @@
 from bfasst.ninja_tools.transform.phys_netlist import PhysNetlist
 from bfasst.paths import NINJA_FLOWS_PATH
 from bfasst.ninja_tools.vivado.synth.vivado_synth import VivadoSynth
+from bfasst.utils.general import ensure
 
 
 class VivadoPhysNetlistXrev(Flow):
@@ -14,7 +15,7 @@ class VivadoPhysNetlistXrev(Flow):
 
     def __init__(self, design, flow_args=None):
         super().__init__(design)
-        self.vivado_synth_tool = VivadoSynth(design, flow_args.get("synth"))
+        self.vivado_synth_tool = VivadoSynth(design, ensure(flow_args, {}).get("synth"))
         self.vivado_impl_tool = VivadoImpl(design)
         self.phys_netlist_tool = PhysNetlist(design)
         self.xrev_tool = Xray(design)
diff --git a/bfasst/ninja_flows/vivado_structural_error_injection.py b/bfasst/ninja_flows/vivado_structural_error_injection.py
index 52665f5a3..23f21ec89 100644
--- a/bfasst/ninja_flows/vivado_structural_error_injection.py
+++ b/bfasst/ninja_flows/vivado_structural_error_injection.py
@@ -10,6 +10,7 @@
 from bfasst.ninja_tools.transform.phys_netlist import PhysNetlist
 from bfasst.paths import NINJA_FLOWS_PATH
 from bfasst.ninja_tools.vivado.synth.vivado_synth import VivadoSynth
+from bfasst.utils.general import ensure
 
 from bfasst.ninja_utils.error_injector import ErrorType
 
@@ -20,7 +21,7 @@ class VivadoStructuralErrorInjection(Flow):
     def __init__(self, design, flow_args=None):
         super().__init__(design)
         random.seed(0)
-        self.vivado_synth_tool = VivadoSynth(design, flow_args.get("synth"))
+        self.vivado_synth_tool = VivadoSynth(design, ensure(flow_args, {}).get("synth"))
         self.vivado_impl_tool = VivadoImpl(design)
         self.phys_netlist_tool = PhysNetlist(design)
         self.xrev_tool = Xray(design)
diff --git a/bfasst/ninja_flows/vivado_yosys_impl.py b/bfasst/ninja_flows/vivado_yosys_impl.py
index 7e4f87d23..0c15405d0 100644
--- a/bfasst/ninja_flows/vivado_yosys_impl.py
+++ b/bfasst/ninja_flows/vivado_yosys_impl.py
@@ -5,6 +5,7 @@
 from bfasst.ninja_tools.rev_bit.xray import Xray
 from bfasst.paths import NINJA_FLOWS_PATH
 from bfasst.ninja_tools.vivado.synth.vivado_synth import VivadoSynth
+from bfasst.utils.general import ensure
 
 
 class VivadoYosysImpl(Flow):
@@ -12,7 +13,7 @@ class VivadoYosysImpl(Flow):
 
     def __init__(self, design, flow_args=None):
         super().__init__(design)
-        self.vivado_synth_tool = VivadoSynth(design, flow_args.get("synth"))
+        self.vivado_synth_tool = VivadoSynth(design, ensure(flow_args, {}).get("synth"))
         self.vivado_impl_tool = VivadoImpl(design)
         self.xrev_tool = Xray(design)
         self.yosys_tool = Yosys(design)
diff --git a/bfasst/utils/general.py b/bfasst/utils/general.py
index dd9ed1020..cbf4c4974 100644
--- a/bfasst/utils/general.py
+++ b/bfasst/utils/general.py
@@ -235,3 +235,10 @@ def ensure_tuple(x):
     if isinstance(x, list):
         return tuple(x)
     return (x,)
+
+
+def ensure(x, y):
+    """Compensates for how python deals with default reference objects"""
+    if x is None:
+        return y
+    return x