diff --git a/scripts/hiddenapi/signature_patterns.py b/scripts/hiddenapi/signature_patterns.py
index 1abdef1..5a82be7 100755
--- a/scripts/hiddenapi/signature_patterns.py
+++ b/scripts/hiddenapi/signature_patterns.py
@@ -60,7 +60,22 @@
     return False
 
 
-def validate_package_prefixes(split_packages, package_prefixes):
+def validate_package_is_not_matched_by_package_prefix(package_type, pkg,
+                                                      package_prefixes):
+    package_prefix = matched_by_package_prefix_pattern(package_prefixes, pkg)
+    if package_prefix:
+        # A package prefix matches the package.
+        package_for_output = slash_package_to_dot_package(pkg)
+        package_prefix_for_output = slash_package_to_dot_package(package_prefix)
+        return [
+            f'{package_type} {package_for_output} is matched by '
+            f'package prefix {package_prefix_for_output}'
+        ]
+    return []
+
+
+def validate_package_prefixes(split_packages, single_packages,
+                              package_prefixes):
     # If there are no package prefixes then there is no possible conflict
     # between them and the split packages.
     if len(package_prefixes) == 0:
@@ -79,17 +94,16 @@
                 f'{package_prefixes_for_output}\n'
                 '    add split_packages:[] to fix')
         else:
-            package_prefix = matched_by_package_prefix_pattern(
-                package_prefixes, split_package)
-            if package_prefix:
-                # A package prefix matches a split package.
-                split_package_for_output = slash_package_to_dot_package(
-                    split_package)
-                package_prefix_for_output = slash_package_to_dot_package(
-                    package_prefix)
-                errors.append(
-                    f'split package {split_package_for_output} is matched by '
-                    f'package prefix {package_prefix_for_output}')
+            errs = validate_package_is_not_matched_by_package_prefix(
+                'split package', split_package, package_prefixes)
+            errors.extend(errs)
+
+    # Check to make sure that the single packages and package prefixes do not
+    # overlap.
+    for single_package in single_packages:
+        errs = validate_package_is_not_matched_by_package_prefix(
+            'single package', single_package, package_prefixes)
+        errors.extend(errs)
     return errors
 
 
@@ -102,21 +116,40 @@
     return errors
 
 
+def validate_single_packages(split_packages, single_packages):
+    overlaps = []
+    for single_package in single_packages:
+        if single_package in split_packages:
+            overlaps.append(single_package)
+    if overlaps:
+        indented = ''.join([f'\n    {o}' for o in overlaps])
+        return [
+            f'single_packages and split_packages overlap, please ensure the '
+            f'following packages are only present in one:{indented}'
+        ]
+    return []
+
+
 def produce_patterns_from_file(file,
                                split_packages=None,
+                               single_packages=None,
                                package_prefixes=None):
     with open(file, 'r', encoding='utf8') as f:
-        return produce_patterns_from_stream(f, split_packages, package_prefixes)
+        return produce_patterns_from_stream(f, split_packages, single_packages,
+                                            package_prefixes)
 
 
 def produce_patterns_from_stream(stream,
                                  split_packages=None,
+                                 single_packages=None,
                                  package_prefixes=None):
     split_packages = set(split_packages or [])
+    single_packages = set(single_packages or [])
     package_prefixes = list(package_prefixes or [])
     # Read in all the signatures into a list and remove any unnecessary class
     # and member names.
     patterns = set()
+    unmatched_packages = set()
     for row in dict_reader(stream):
         signature = row['signature']
         text = signature.removeprefix('L')
@@ -138,11 +171,31 @@
             # Remove inner class names.
             pieces = qualified_class_name.split('$', maxsplit=1)
             pattern = pieces[0]
-        else:
+            patterns.add(pattern)
+        elif pkg in single_packages:
             # Add a * to ensure that the pattern matches the classes in that
             # package.
             pattern = pkg + '/*'
-        patterns.add(pattern)
+            patterns.add(pattern)
+        else:
+            unmatched_packages.add(pkg)
+
+    # Remove any unmatched packages that would be matched by a package prefix
+    # pattern.
+    unmatched_packages = [
+        p for p in unmatched_packages
+        if not matched_by_package_prefix_pattern(package_prefixes, p)
+    ]
+    errors = []
+    if unmatched_packages:
+        unmatched_packages.sort()
+        indented = ''.join([
+            f'\n    {slash_package_to_dot_package(p)}'
+            for p in unmatched_packages
+        ])
+        errors.append('The following packages were unexpected, please add them '
+                      'to one of the hidden_api properties, split_packages, '
+                      f'single_packages or package_prefixes:{indented}')
 
     # Remove any patterns that would be matched by a package prefix pattern.
     patterns = [
@@ -155,7 +208,13 @@
     patterns = patterns + [f'{p}/**' for p in package_prefixes]
     # Sort the patterns.
     patterns.sort()
-    return patterns
+    return patterns, errors
+
+
+def print_and_exit(errors):
+    for error in errors:
+        print(error)
+    sys.exit(1)
 
 
 def main(args):
@@ -175,26 +234,41 @@
         '--package-prefix',
         action='append',
         help='A package prefix unique to this set of flags')
+    args_parser.add_argument(
+        '--single-package',
+        action='append',
+        help='A single package unique to this set of flags')
     args_parser.add_argument('--output', help='Generated signature prefixes')
     args = args_parser.parse_args(args)
 
     split_packages = set(
         dot_packages_to_slash_packages(args.split_package or []))
     errors = validate_split_packages(split_packages)
+    if errors:
+        print_and_exit(errors)
+
+    single_packages = list(
+        dot_packages_to_slash_packages(args.single_package or []))
+
+    errors = validate_single_packages(split_packages, single_packages)
+    if errors:
+        print_and_exit(errors)
 
     package_prefixes = dot_packages_to_slash_packages(args.package_prefix or [])
 
-    if not errors:
-        errors = validate_package_prefixes(split_packages, package_prefixes)
+    errors = validate_package_prefixes(split_packages, single_packages,
+                                       package_prefixes)
+    if errors:
+        print_and_exit(errors)
+
+    patterns = []
+    # Read in all the patterns into a list.
+    patterns, errors = produce_patterns_from_file(args.flags, split_packages,
+                                                  single_packages,
+                                                  package_prefixes)
 
     if errors:
-        for error in errors:
-            print(error)
-        sys.exit(1)
-
-    # Read in all the patterns into a list.
-    patterns = produce_patterns_from_file(args.flags, split_packages,
-                                          package_prefixes)
+        print_and_exit(errors)
 
     # Write out all the patterns.
     with open(args.output, 'w', encoding='utf8') as outputFile:
diff --git a/scripts/hiddenapi/signature_patterns_test.py b/scripts/hiddenapi/signature_patterns_test.py
index 5c5635c..90b3d0b 100755
--- a/scripts/hiddenapi/signature_patterns_test.py
+++ b/scripts/hiddenapi/signature_patterns_test.py
@@ -32,22 +32,37 @@
     @staticmethod
     def produce_patterns_from_string(csv_text,
                                      split_packages=None,
+                                     single_packages=None,
                                      package_prefixes=None):
         with io.StringIO(csv_text) as f:
             return signature_patterns.produce_patterns_from_stream(
-                f, split_packages, package_prefixes)
+                f, split_packages, single_packages, package_prefixes)
+
+    def test_generate_unmatched(self):
+        _, errors = self.produce_patterns_from_string(
+            TestGeneratedPatterns.csv_flags)
+        self.assertEqual([
+            'The following packages were unexpected, please add them to one of '
+            'the hidden_api properties, split_packages, single_packages or '
+            'package_prefixes:\n'
+            '    java.lang'
+        ], errors)
 
     def test_generate_default(self):
-        patterns = self.produce_patterns_from_string(
-            TestGeneratedPatterns.csv_flags)
+        patterns, errors = self.produce_patterns_from_string(
+            TestGeneratedPatterns.csv_flags, single_packages=['java/lang'])
+        self.assertEqual([], errors)
+
         expected = [
             'java/lang/*',
         ]
         self.assertEqual(expected, patterns)
 
     def test_generate_split_package(self):
-        patterns = self.produce_patterns_from_string(
+        patterns, errors = self.produce_patterns_from_string(
             TestGeneratedPatterns.csv_flags, split_packages={'java/lang'})
+        self.assertEqual([], errors)
+
         expected = [
             'java/lang/Character',
             'java/lang/Object',
@@ -56,8 +71,10 @@
         self.assertEqual(expected, patterns)
 
     def test_generate_split_package_wildcard(self):
-        patterns = self.produce_patterns_from_string(
+        patterns, errors = self.produce_patterns_from_string(
             TestGeneratedPatterns.csv_flags, split_packages={'*'})
+        self.assertEqual([], errors)
+
         expected = [
             'java/lang/Character',
             'java/lang/Object',
@@ -66,16 +83,20 @@
         self.assertEqual(expected, patterns)
 
     def test_generate_package_prefix(self):
-        patterns = self.produce_patterns_from_string(
+        patterns, errors = self.produce_patterns_from_string(
             TestGeneratedPatterns.csv_flags, package_prefixes={'java/lang'})
+        self.assertEqual([], errors)
+
         expected = [
             'java/lang/**',
         ]
         self.assertEqual(expected, patterns)
 
     def test_generate_package_prefix_top_package(self):
-        patterns = self.produce_patterns_from_string(
+        patterns, errors = self.produce_patterns_from_string(
             TestGeneratedPatterns.csv_flags, package_prefixes={'java'})
+        self.assertEqual([], errors)
+
         expected = [
             'java/**',
         ]
@@ -92,21 +113,38 @@
 
     def test_split_package_wildcard_conflicts_with_package_prefixes(self):
         errors = signature_patterns.validate_package_prefixes(
-            {'*'}, package_prefixes={'java'})
+            {'*'}, [], package_prefixes={'java'})
         expected = [
             "split package '*' conflicts with all package prefixes java\n"
             '    add split_packages:[] to fix',
         ]
         self.assertEqual(expected, errors)
 
-    def test_split_package_conflict(self):
+    def test_split_package_conflicts_with_package_prefixes(self):
         errors = signature_patterns.validate_package_prefixes(
-            {'java/split'}, package_prefixes={'java'})
+            {'java/split'}, [], package_prefixes={'java'})
         expected = [
             'split package java.split is matched by package prefix java',
         ]
         self.assertEqual(expected, errors)
 
+    def test_single_package_conflicts_with_package_prefixes(self):
+        errors = signature_patterns.validate_package_prefixes(
+            {}, ['java/single'], package_prefixes={'java'})
+        expected = [
+            'single package java.single is matched by package prefix java',
+        ]
+        self.assertEqual(expected, errors)
+
+    def test_single_package_conflicts_with_split_packages(self):
+        errors = signature_patterns.validate_single_packages({'java/pkg'},
+                                                             ['java/pkg'])
+        expected = [
+            'single_packages and split_packages overlap, please ensure the '
+            'following packages are only present in one:\n    java/pkg'
+        ]
+        self.assertEqual(expected, errors)
+
 
 if __name__ == '__main__':
     unittest.main(verbosity=2)