diff --git a/f4pga/flows/common.py b/f4pga/flows/common.py
index fb89da2..e024be6 100644
--- a/f4pga/flows/common.py
+++ b/f4pga/flows/common.py
@@ -179,7 +179,7 @@ def vpr(mode: str, vprargs: VprArgs, cwd=None):
     )
 
 
-_vpr_specific_values = [
+vpr_specific_values = [
     "arch_def",
     "rr_graph_lookahead_bin",
     "rr_graph_real_bin",
@@ -189,11 +189,6 @@ _vpr_specific_values = [
 ]
 
 
-def vpr_specific_values():
-    global _vpr_specific_values
-    return _vpr_specific_values
-
-
 def options_dict_to_list(opt_dict: dict):
     """
     Converts a dictionary of named options for CLI program to a list.
diff --git a/f4pga/flows/modules/analysis.py b/f4pga/flows/modules/analysis.py
index 40d2115..eb8a196 100644
--- a/f4pga/flows/modules/analysis.py
+++ b/f4pga/flows/modules/analysis.py
@@ -72,7 +72,7 @@ class analysisModule(Module):
         self.no_of_phases = 2
         self.takes = ["eblif", "route", "sdc?"]
         self.produces = ["merged_post_implementation_v", "post_implementation_v", "analysis_log"]
-        self.values = ["device", "vpr_options?"] + vpr_specific_values()
+        self.values = ["device", "vpr_options?"] + vpr_specific_values
 
 
 ModuleClass = analysisModule
diff --git a/f4pga/flows/modules/fasm.py b/f4pga/flows/modules/fasm.py
index 3ac06bb..8c61dbb 100644
--- a/f4pga/flows/modules/fasm.py
+++ b/f4pga/flows/modules/fasm.py
@@ -81,7 +81,7 @@ class FasmModule(Module):
         self.no_of_phases = 2
         self.takes = ["eblif", "net", "place", "route", "fasm_extra?", "sdc?"]
         self.produces = ["fasm"]
-        self.values = ["device", "top", "pnr_corner?"] + vpr_specific_values()
+        self.values = ["device", "top", "pnr_corner?"] + vpr_specific_values
         self.prod_meta = {"fasm": "FPGA assembly file"}
 
 
diff --git a/f4pga/flows/modules/pack.py b/f4pga/flows/modules/pack.py
index 4c01dae..0d90fe1 100644
--- a/f4pga/flows/modules/pack.py
+++ b/f4pga/flows/modules/pack.py
@@ -77,9 +77,7 @@ class PackModule(Module):
         self.no_of_phases = 2
         self.takes = ["eblif", "sdc?"]
         self.produces = ["net", "util_rpt", "timing_rpt", "pack_log!"]
-        self.values = [
-            "device",
-        ] + vpr_specific_values()
+        self.values = ["device"] + vpr_specific_values
 
 
 ModuleClass = PackModule
diff --git a/f4pga/flows/modules/place.py b/f4pga/flows/modules/place.py
index e3f5aab..4962786 100644
--- a/f4pga/flows/modules/place.py
+++ b/f4pga/flows/modules/place.py
@@ -82,7 +82,7 @@ class PlaceModule(Module):
         self.no_of_phases = 2
         self.takes = ["build_dir", "eblif", "sdc?", "place_constraints?", "io_place?"]
         self.produces = ["place"]
-        self.values = ["device", "vpr_options?"] + vpr_specific_values()
+        self.values = ["device", "vpr_options?"] + vpr_specific_values
 
 
 ModuleClass = PlaceModule
diff --git a/f4pga/flows/modules/route.py b/f4pga/flows/modules/route.py
index 5d08582..91ed793 100644
--- a/f4pga/flows/modules/route.py
+++ b/f4pga/flows/modules/route.py
@@ -62,7 +62,7 @@ class RouteModule(Module):
         self.no_of_phases = 2
         self.takes = ["eblif", "place", "sdc?"]
         self.produces = ["route"]
-        self.values = ["device", "vpr_options?"] + vpr_specific_values()
+        self.values = ["device", "vpr_options?"] + vpr_specific_values
 
 
 ModuleClass = RouteModule