diff --git a/SConstruct b/SConstruct
index e7fa4b53b7..69c941a078 100755
--- a/SConstruct
+++ b/SConstruct
@@ -240,27 +240,9 @@ def makePathListAbsolute(path_list, root=GetLaunchDir()):
 # doesn't work (obviously!).
 BUILD_TARGETS[:] = makePathListAbsolute(BUILD_TARGETS)
 
-# Generate a list of the unique build roots and configs that the
-# collected targets reference.
-variant_paths = set()
-build_root = None
-for t in BUILD_TARGETS:
-    this_build_root, variant = parse_build_path(t)
-
-    # Make sure all targets use the same build root.
-    if not build_root:
-        build_root = this_build_root
-    elif this_build_root != build_root:
-        error("build targets not under same build root\n  %s\n  %s" %
-            (build_root, this_build_root))
-
-    # Collect all the variants into a set.
-    variant_paths.add(os.path.join('/', build_root, variant))
-
-# Make sure build_root exists (might not if this is the first build there)
-if not isdir(build_root):
-    mkdir(build_root)
-main['BUILDROOT'] = build_root
+# Generate a list of the unique build directories that the collected targets
+# reference.
+variant_paths = set(map(parse_build_path, BUILD_TARGETS))
 
 
 ########################################################################
@@ -395,7 +377,7 @@ for variant_path in variant_paths:
     env = main.Clone()
     env['BUILDDIR'] = variant_path
 
-    gem5_build = os.path.join(build_root, variant_path, 'gem5.build')
+    gem5_build = os.path.join(variant_path, 'gem5.build')
     env['GEM5BUILD'] = gem5_build
     Execute(Mkdir(gem5_build))
 
diff --git a/site_scons/gem5_scons/__init__.py b/site_scons/gem5_scons/__init__.py
index c93a5e29e0..3638d9c561 100644
--- a/site_scons/gem5_scons/__init__.py
+++ b/site_scons/gem5_scons/__init__.py
@@ -39,6 +39,7 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 import os
+import os.path
 import pickle
 import sys
 import tempfile
@@ -56,7 +57,7 @@ termcap = get_termcap()
 def strip_build_path(path, env):
     path = str(path)
     build_base = "build/"
-    variant_base = env["BUILDROOT"] + os.path.sep
+    variant_base = os.path.dirname(env["BUILDDIR"]) + os.path.sep
     if path.startswith(variant_base):
         path = path[len(variant_base) :]
     elif path.startswith(build_base):
@@ -117,7 +118,7 @@ class Transform:
         source = source[0 : self.max_sources]
 
         def strip(f):
-            return strip_build_path(str(f), env)
+            return strip_build_path(f, env)
 
         if len(source) > 0:
             srcs = list(map(strip, source))
@@ -255,18 +256,21 @@ def error(*args, **kwargs):
 def parse_build_path(target):
     path_dirs = target.split("/")
 
-    # Pop off the target file.
-    path_dirs.pop()
-
-    # Search backwards for the "build" directory. Whatever was just before it
-    # was the name of the variant.
-    variant_dir = path_dirs.pop()
-    while path_dirs and path_dirs[-1] != "build":
-        variant_dir = path_dirs.pop()
-    if not path_dirs:
-        error("No non-leaf 'build' dir found on target path.", target)
-
-    return os.path.join("/", *path_dirs), variant_dir
+    # Search backwards for a directory with a gem5.build sub-directory, or a
+    # directory who's parent is called "build". gem5.build identifies an
+    # existing gem5 build directory. A directory called "build" is an anchor
+    # for a legacy "build/${VARIANT}/${TARGET}" style build path, where the
+    # variant selects a default config to use.
+    while path_dirs:
+        dot_gem5 = os.path.join("/", *path_dirs, "gem5.build")
+        if (
+            os.path.isdir(dot_gem5)
+            or len(path_dirs) > 1
+            and path_dirs[-2] == "build"
+        ):
+            return os.path.join("/", *path_dirs)
+        path_dirs.pop()
+    error(f"No existing build directory and no variant for {target}")
 
 
 # The MakeAction wrapper, and a SCons tool to set up the *COMSTR variables.