diff --git a/Lib/fontTools/varLib/__init__.py b/Lib/fontTools/varLib/__init__.py
index 9bae80d12..d965e8884 100644
--- a/Lib/fontTools/varLib/__init__.py
+++ b/Lib/fontTools/varLib/__init__.py
@@ -39,13 +39,11 @@ import os.path
 import logging
 from copy import deepcopy
 from pprint import pformat
+from .errors import VarLibError, VarLibValidationError
 
 log = logging.getLogger("fontTools.varLib")
 
 
-class VarLibError(Exception):
-	pass
-
 #
 # Creation routines
 #
@@ -703,7 +701,7 @@ def load_designspace(designspace):
 
 	masters = ds.sources
 	if not masters:
-		raise VarLibError("no sources found in .designspace")
+		raise VarLibValidationError("Designspace must have at least one source.")
 	instances = ds.instances
 
 	standard_axis_map = OrderedDict([
@@ -927,7 +925,7 @@ def _open_font(path, master_finder=lambda s: s):
 	elif tp in ("TTF", "OTF", "WOFF", "WOFF2"):
 		font = TTFont(master_path)
 	else:
-		raise VarLibError("Invalid master path: %r" % master_path)
+		raise VarLibValidationError("Invalid master path: %r" % master_path)
 	return font
 
 
@@ -947,10 +945,10 @@ def load_masters(designspace, master_finder=lambda s: s):
 		# If a SourceDescriptor has a layer name, demand that the compiled TTFont
 		# be supplied by the caller. This spares us from modifying MasterFinder.
 		if master.layerName and master.font is None:
-			raise AttributeError(
-				"Designspace source '%s' specified a layer name but lacks the "
-				"required TTFont object in the 'font' attribute."
-				% (master.name or "<Unknown>")
+			raise VarLibValidationError(
+				f"Designspace source '{master.name or '<Unknown>'}' specified a "
+				"layer name but lacks the required TTFont object in the 'font' "
+				"attribute."
 			)
 
 	return designspace.loadSourceFonts(_open_font, master_finder=master_finder)
diff --git a/Tests/varLib/varLib_test.py b/Tests/varLib/varLib_test.py
index b1faa50b0..a663eaeb4 100644
--- a/Tests/varLib/varLib_test.py
+++ b/Tests/varLib/varLib_test.py
@@ -1,6 +1,7 @@
 from fontTools.misc.py23 import *
 from fontTools.ttLib import TTFont, newTable
 from fontTools.varLib import build, load_designspace
+from fontTools.varLib.errors import VarLibValidationError
 from fontTools.varLib.mutator import instantiateVariableFont
 from fontTools.varLib import main as varLib_main, load_masters
 from fontTools.varLib import set_default_weight_width_slant
@@ -744,7 +745,7 @@ def test_load_masters_layerName_without_required_font():
     ds.addSource(s)
 
     with pytest.raises(
-        AttributeError,
+        VarLibValidationError,
         match="specified a layer name but lacks the required TTFont object",
     ):
         load_masters(ds)