diff --git a/alibuild_helpers/utilities.py b/alibuild_helpers/utilities.py
index a78c175e..2cfb4e1c 100644
--- a/alibuild_helpers/utilities.py
+++ b/alibuild_helpers/utilities.py
@@ -261,16 +261,24 @@ def detectArch():
   except:
     return doDetectArch(hasOsRelease, osReleaseLines, ["unknown", "", ""], "", "")
 
-def filterByArchitecture(arch, requires):
+def filterByArchitectureDefaults(arch, defaults, requires):
   for r in requires:
     require, matcher = ":" in r and r.split(":", 1) or (r, ".*")
+    if matcher.startswith("defaults="):
+      wanted = matcher[len("defaults="):]
+      if re.match(wanted, defaults):
+        yield require
     if re.match(matcher, arch):
       yield require
 
-def disabledByArchitecture(arch, requires):
+def disabledByArchitectureDefaults(arch, defaults, requires):
   for r in requires:
     require, matcher = ":" in r and r.split(":", 1) or (r, ".*")
-    if not re.match(matcher, arch):
+    if matcher.startswith("defaults="):
+      wanted = matcher[len("defaults="):]
+      if not re.match(wanted, defaults):
+        yield require
+    elif not re.match(matcher, arch):
       yield require
 
 def readDefaults(configDir, defaults, error, architecture):
@@ -543,10 +551,10 @@ def getPackageList(packages, specs, configDir, preferSystem, noSystem,
           validDefaults = None  # no valid default works for all current packages
 
     # For the moment we treat build_requires just as requires.
-    fn = lambda what: disabledByArchitecture(architecture, spec.get(what, []))
+    fn = lambda what: disabledByArchitectureDefaults(architecture, defaults, spec.get(what, []))
     spec["disabled"] += [x for x in fn("requires")]
     spec["disabled"] += [x for x in fn("build_requires")]
-    fn = lambda what: filterByArchitecture(architecture, spec.get(what, []))
+    fn = lambda what: filterByArchitectureDefaults(architecture, defaults, spec.get(what, []))
     spec["requires"] = [x for x in fn("requires") if not x in disable]
     spec["build_requires"] = [x for x in fn("build_requires") if not x in disable]
     if spec["package"] != "defaults-release":
diff --git a/docs/docs/reference.md b/docs/docs/reference.md
index a341be80..3ad39a61 100644
--- a/docs/docs/reference.md
+++ b/docs/docs/reference.md
@@ -130,7 +130,10 @@ The following entries are optional in the header:
 
     The specified dependencies will be built before building the given package.
     You can specify platform-specific dependencies by appending `:<regexp>` to
-    the dependency name. Such a regular expression will be matched against the
+    the dependency name. Similarly, you can specify build default specific dependencies
+    by appending `:defaults=<regex>`.
+
+    Such a regular expression will be matched against the
     architecture provided via `--architecture`, and if it does not match, the
     requirement will not be included. For instance:
 
diff --git a/tests/test_utilities.py b/tests/test_utilities.py
index 3fc2beef..1667b3e7 100644
--- a/tests/test_utilities.py
+++ b/tests/test_utilities.py
@@ -5,7 +5,7 @@
 # Assuming you are using the mock library to ... mock things
 from unittest.mock import patch
 
-from alibuild_helpers.utilities import doDetectArch, filterByArchitecture
+from alibuild_helpers.utilities import doDetectArch, filterByArchitectureDefaults, disabledByArchitectureDefaults
 from alibuild_helpers.utilities import Hasher
 from alibuild_helpers.utilities import asList
 from alibuild_helpers.utilities import prunePaths
@@ -175,12 +175,24 @@ def test_asList(self):
     self.assertEqual(asList(None), [None])
 
   def test_filterByArchitecture(self):
-    self.assertEqual(["AliRoot"], list(filterByArchitecture("osx_x86-64", ["AliRoot"])))
-    self.assertEqual([], list(filterByArchitecture("osx_x86-64", ["AliRoot:(?!osx)"])))
-    self.assertEqual(["GCC"], list(filterByArchitecture("osx_x86-64", ["AliRoot:(?!osx)", "GCC"])))
-    self.assertEqual(["AliRoot", "GCC"], list(filterByArchitecture("osx_x86-64", ["AliRoot:(?!slc6)", "GCC"])))
-    self.assertEqual(["GCC"], list(filterByArchitecture("osx_x86-64", ["AliRoot:slc6", "GCC:osx"])))
-    self.assertEqual([], list(filterByArchitecture("osx_x86-64", [])))
+    self.assertEqual(["AliRoot"], list(filterByArchitectureDefaults("osx_x86-64", "ali", ["AliRoot"])))
+    self.assertEqual([], list(filterByArchitectureDefaults("osx_x86-64", "ali", ["AliRoot:(?!osx)"])))
+    self.assertEqual(["GCC"], list(filterByArchitectureDefaults("osx_x86-64", "ali", ["AliRoot:(?!osx)", "GCC"])))
+    self.assertEqual(["AliRoot", "GCC"], list(filterByArchitectureDefaults("osx_x86-64", "ali", ["AliRoot:(?!slc6)", "GCC"])))
+    self.assertEqual(["GCC"], list(filterByArchitectureDefaults("osx_x86-64", "ali", ["AliRoot:slc6", "GCC:osx"])))
+    self.assertEqual([], list(filterByArchitectureDefaults("osx_x86-64", "ali", [])))
+    self.assertEqual(["GCC"], list(filterByArchitectureDefaults("osx_x86-64", "ali", ["AliRoot:slc6", "GCC:defaults=ali"])))
+    self.assertEqual([], list(filterByArchitectureDefaults("osx_x86-64", "o2", ["AliRoot:slc6", "GCC:defaults=ali"])))
+
+  def test_disabledByArchitecture(self):
+    self.assertEqual([], list(disabledByArchitectureDefaults("osx_x86-64", "ali", ["AliRoot"])))
+    self.assertEqual(["AliRoot"], list(disabledByArchitectureDefaults("osx_x86-64", "ali", ["AliRoot:(?!osx)"])))
+    self.assertEqual(["AliRoot"], list(disabledByArchitectureDefaults("osx_x86-64", "ali", ["AliRoot:(?!osx)", "GCC"])))
+    self.assertEqual([], list(disabledByArchitectureDefaults("osx_x86-64", "ali", ["AliRoot:(?!slc6)", "GCC"])))
+    self.assertEqual(["AliRoot"], list(disabledByArchitectureDefaults("osx_x86-64", "ali", ["AliRoot:slc6", "GCC:osx"])))
+    self.assertEqual([], list(disabledByArchitectureDefaults("osx_x86-64", "ali", [])))
+    self.assertEqual(["AliRoot"], list(disabledByArchitectureDefaults("osx_x86-64", "ali", ["AliRoot:slc6", "GCC:defaults=ali"])))
+    self.assertEqual(["AliRoot", "GCC"], list(disabledByArchitectureDefaults("osx_x86-64", "o2", ["AliRoot:slc6", "GCC:defaults=ali"])))
 
   def test_prunePaths(self):
     fake_env = {