diff --git a/BaseTools/set_vsprefix_envs.bat b/BaseTools/set_vsprefix_envs.bat
index df2c771951..5565f615f1 100644
--- a/BaseTools/set_vsprefix_envs.bat
+++ b/BaseTools/set_vsprefix_envs.bat
@@ -242,7 +242,12 @@ if not defined WINDDK3790_PREFIX (
 )
 
 if not defined IASL_PREFIX (
-  set IASL_PREFIX=C:\ASL\
+  if exist "C:\ASL\" (
+    set IASL_PREFIX=C:\ASL\
+  ) else (
+      @echo.
+      @echo !!! WARNING !!! IASL_PREFIX environment variable is not set
+  )
 )
 
 popd
diff --git a/BaseTools/toolsetup.bat b/BaseTools/toolsetup.bat
index ac52f7a8ee..92eb6823a1 100755
--- a/BaseTools/toolsetup.bat
+++ b/BaseTools/toolsetup.bat
@@ -333,6 +333,17 @@ if defined VS2022 (
   call %EDK_TOOLS_PATH%\set_vsprefix_envs.bat
   call %EDK_TOOLS_PATH%\get_vsvars.bat
 )
+if defined BASETOOLS_MINGW_BUILD (
+  if not defined IASL_PREFIX (
+    REM For VS builds this environment variable is set via set_vsprefix_envs.bat
+    if exist "C:\ASL\" (
+      set IASL_PREFIX=C:\ASL\
+    ) else (
+        @echo.
+        @echo !!! WARNING !!! IASL_PREFIX environment variable is not set
+    )
+  )
+)
 if %SCRIPT_ERROR% NEQ 0 (
   @echo.
   @echo !!! ERROR !!! %VSTool% is not installed !!!