diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 78292f20ac2e..ecf6702c4382 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -2283,13 +2283,12 @@ def get_all_link_deps(self):
         return []
 
     def is_internal(self) -> bool:
-        if not self.should_install():
-            return True
-        for out in self.get_outputs():
-            # Can't check if this is a static library, so try to guess
-            if not out.endswith(('.a', '.lib')):
-                return False
-        return True
+        '''
+        Returns True iif this is a not installed static library.
+        '''
+        if len(self.outputs) != 1:
+            return False
+        return CustomTargetIndex(self, self.outputs[0]).is_internal()
 
     def extract_all_objects_recurse(self):
         return self.get_outputs()
@@ -2443,7 +2442,11 @@ def should_install(self) -> bool:
         return self.target.should_install()
 
     def is_internal(self) -> bool:
-        return self.target.is_internal()
+        '''
+        Returns True iif this is a not installed static library
+        '''
+        suf = os.path.splitext(self.output)[-1]
+        return (suf == '.a' or suf == '.lib') and not self.should_install()
 
     def extract_all_objects_recurse(self):
         return self.target.extract_all_objects_recurse()
diff --git a/mesonbuild/modules/pkgconfig.py b/mesonbuild/modules/pkgconfig.py
index 62e1c1595cae..c1f31cd72932 100644
--- a/mesonbuild/modules/pkgconfig.py
+++ b/mesonbuild/modules/pkgconfig.py
@@ -186,7 +186,8 @@ def _add_link_whole(self, t, public):
         # lists in case a library is link_with and link_whole at the same time.
         # See remove_dups() below.
         self.link_whole_targets.append(t)
-        self._add_lib_dependencies(t.link_targets, t.link_whole_targets, t.external_deps, public)
+        if isinstance(t, build.BuildTarget):
+            self._add_lib_dependencies(t.link_targets, t.link_whole_targets, t.external_deps, public)
 
     def add_version_reqs(self, name, version_reqs):
         if version_reqs:
diff --git a/test cases/common/45 pkgconfig-gen/meson.build b/test cases/common/45 pkgconfig-gen/meson.build
index 4638123cf1e8..1cb55e9061ee 100644
--- a/test cases/common/45 pkgconfig-gen/meson.build	
+++ b/test cases/common/45 pkgconfig-gen/meson.build	
@@ -18,6 +18,8 @@ if v.version_compare('<0.29')
   error('MESON_SKIP_TEST: pkg-config version \'' + v + '\' too old')
 endif
 
+python = import('python').find_installation()
+fs = import('fs')
 pkgg = import('pkgconfig')
 
 lib = shared_library('simple', 'simple.c')
@@ -96,3 +98,17 @@ stat2 = static_library('stat2', 'simple.c', install: true)
 simple4 = library('simple4', 'simple.c', link_with: stat2)
 simple5 = library('simple5', 'simple5.c', link_with: simple4, link_whole: stat2)
 pkgg.generate(simple5)
+
+# Regression test: A library linking to an uninstalled custom_target static
+# library used to crash when generating its pkgconfig file.
+# Copy libstat2.a to libstat3.a to have a static library as custom target.
+infile = stat2.full_path()
+outfile = meson.current_build_dir() / 'libstat3.a'
+script = 'import shutil ; shutil.copyfile("@0@", "@1@")'.format(infile, outfile)
+ct = custom_target('stat3',
+  input: stat2,
+  output: fs.name(outfile),
+  command: [python, '-c', script],
+)
+simple6 = library('simple6', link_with: ct)
+pkgg.generate(simple6)