diff --git a/litex/build/xilinx/ise.py b/litex/build/xilinx/ise.py
index 4e9045998..34b82ae30 100644
--- a/litex/build/xilinx/ise.py
+++ b/litex/build/xilinx/ise.py
@@ -115,9 +115,8 @@ def _run_ise(build_name, mode, ngdbuild_opt, toolchain, platform):
         script_ext = ".sh"
         shell = ["bash"]
         build_script_contents = "# Autogenerated by LiteX / git: " + tools.get_litex_git_revision() + "\nset -e\n"
-        litex_env_ise = os.getenv("LITEX_ENV_ISE", None)
-        if litex_env_ise is not None:
-            build_script_contents += "source " + os.path.join(litex_env_ise, "settings64.sh\n")
+        if os.getenv("LITEX_ENV_ISE", False):
+            build_script_contents += "source " + os.path.join(os.getenv("LITEX_ENV_ISE"), "settings64.sh\n")
         fail_stmt = ""
     if mode == "edif":
         ext = "ngo"
diff --git a/litex/build/xilinx/vivado.py b/litex/build/xilinx/vivado.py
index 2f707e2d4..d81c682d6 100644
--- a/litex/build/xilinx/vivado.py
+++ b/litex/build/xilinx/vivado.py
@@ -73,9 +73,8 @@ def _build_script(build_name):
         tools.write_to_file(script_file, script_contents)
     else:
         script_contents = "# Autogenerated by LiteX / git: " + tools.get_litex_git_revision() + "\nset -e\n"
-        litex_env_vivado = os.getenv("LITEX_ENV_VIVADO", None)
-        if litex_env_vivado is not None:
-            script_contents += "source " + os.path.join(litex_env_vivado, "settings64.sh\n")
+        if os.getenv("LITEX_ENV_VIVADO", False):
+            script_contents += "source " + os.path.join(os.getenv("LITEX_ENV_VIVADO"), "settings64.sh\n")
         script_contents += "vivado -mode batch -source " + build_name + ".tcl\n"
         script_file = "build_" + build_name + ".sh"
         tools.write_to_file(script_file, script_contents)