diff --git a/conda/meta.yaml b/conda/meta.yaml
index 5b67a99..6262240 100644
--- a/conda/meta.yaml
+++ b/conda/meta.yaml
@@ -19,7 +19,7 @@ build:
   script:
     - readlink -f "$(which g++)"         # [linux]
     - g++ --version                      # [linux]
-    - sip-install --verbose
+    - {{ PYTHON }} -m pip install . -vv --no-deps --no-build-isolation
   script_env:
     - SETUPTOOLS_SCM_PRETEND_VERSION
 
@@ -42,14 +42,12 @@ requirements:
     - qt-main
     - libqglviewer
     - libgl-devel                        # [linux]
-    - xorg-libxfixes                     # [linux]
 
   run:
     - python
     - pyqt
     - libqglviewer
     - pyopengl
-    - xorg-libxfixes  # [linux]
 
 test:
   requires:
diff --git a/environment-linux.yml b/environment-linux.yml
index 4a190e1..6131fb3 100644
--- a/environment-linux.yml
+++ b/environment-linux.yml
@@ -23,7 +23,6 @@ dependencies:
     - qt-main
     - libqglviewer
     - libgl-devel
-    - xorg-libxfixes
     # run
     - pyopengl
     # test
diff --git a/project.py b/project.py
index f0eda41..6ff98a7 100644
--- a/project.py
+++ b/project.py
@@ -69,23 +69,16 @@ def __init__(self, project):
 
     def apply_user_defaults(self, tool):
 
+        # Libraries are declared in pyproject.toml. Qt only adds its own include
+        # dirs and links its libraries by full path, so the dirs of the conda env
+        # are needed to find libQGLViewer and GLU headers and libraries.
         system = platform.system()
         prefix = os.environ.get("PREFIX") or os.environ.get("CONDA_PREFIX")
-        
-        if system in ('Darwin','Linux') :
-            self.libraries.append('QGLViewer')
-            if prefix:
-                self.include_dirs.append(f'{prefix}/include')
-                self.library_dirs.append(f'{prefix}/lib')
-
-        if system == 'Linux':
-            self.libraries.append('GLU')
-
-        elif system == 'Windows':
-            self.libraries.append('QGLViewer2')
-            self.libraries.append('opengl32')
-            self.libraries.append('glu32')
-        
+
+        if system in ('Darwin','Linux') and prefix:
+            self.include_dirs.append(f'{prefix}/include')
+            self.library_dirs.append(f'{prefix}/lib')
+
         self.define_macros.append('PYQGLVIEWER_VERSION="'+PYQGLVIEWER_VERSION+'"')
         
         super().apply_user_defaults(tool)
diff --git a/pyproject.toml b/pyproject.toml
index cac2451..c6be824 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,7 +1,9 @@
  # Specify the build system.
 [build-system]
 # "setuptools", "setuptools-scm" not used
-requires = ["sip<=6.10", "PyQt-builder=1.18"]
+# Not installed nor checked by pip with --no-build-isolation: the versions that work
+# (sip<=6.10, PyQt-builder 1.18.*) are pinned in conda/meta.yaml
+requires = ["sip", "PyQt-builder"]
 build-backend = "sipbuild.api"
 
 
@@ -27,7 +29,12 @@ sip-files-dir = "sip"
 [tool.sip.bindings.PyQGLViewer]
 qmake-QT = ['xml', 'opengl', 'gui', 'widgets']
 tags = ['QGLViewer_2_9_1']
-
-
-# Could specified directly with new construct but currently only working on MacOS. Instead options set in project.py
-# libraries = ['QGLViewer ; system_platform == "Linux"','GLU  ; system_platform == "Linux"']
\ No newline at end of file
+# Markers must follow the name without space ('name;marker'): sip keeps spaces in the
+# value. Include and library dirs of the conda env are added in project.py.
+libraries = [
+    'QGLViewer;sys_platform != "win32"',
+    'GLU;sys_platform == "linux"',
+    'QGLViewer2;sys_platform == "win32"',
+    'opengl32;sys_platform == "win32"',
+    'glu32;sys_platform == "win32"',
+]