diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8dacec9..c9be314 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -391,7 +391,7 @@ jobs:
           - throw_exception
           - uuid
 
-        args: [ '' ]
+        args: [ '', '-C' ]
 
     runs-on: ubuntu-latest
 
diff --git a/depinst/depinst.py b/depinst/depinst.py
index 6dfba36..7f759aa 100644
--- a/depinst/depinst.py
+++ b/depinst/depinst.py
@@ -70,7 +70,7 @@ def module_for_header( h, x, gm ):
         return None
 
 
-def scan_header_dependencies( f, x, gm, deps ):
+def scan_header_dependencies( f, x, gm, deps, dep_path ):
 
     for line in f:
 
@@ -89,8 +89,13 @@ def scan_header_dependencies( f, x, gm, deps ):
                     vprint( 1, 'Adding dependency', mod )
                     deps[ mod ] = 0
 
+                elif len(dep_path) > 1 and mod == dep_path[0]:
 
-def scan_directory( d, x, gm, deps ):
+                    dep_path = dep_path + [ mod ]
+                    raise DependencyCycle( 'Dependency cycle detected: ' + ' -> '.join(dep_path) )
+
+
+def scan_directory( d, x, gm, deps, dep_path ):
 
     vprint( 1, 'Scanning directory', d )
 
@@ -108,20 +113,20 @@ def scan_directory( d, x, gm, deps ):
             if sys.version_info[0] < 3:
 
                 with open( fn, 'r' ) as f:
-                    scan_header_dependencies( f, x, gm, deps )
+                    scan_header_dependencies( f, x, gm, deps, dep_path )
 
             else:
 
                 with open( fn, 'r', encoding='latin-1' ) as f:
-                    scan_header_dependencies( f, x, gm, deps )
+                    scan_header_dependencies( f, x, gm, deps, dep_path )
 
 
-def scan_module_dependencies( m, x, gm, deps, dirs ):
+def scan_module_dependencies( m, x, gm, deps, dirs, dep_path ):
 
     vprint( 1, 'Scanning module', m )
 
     for dir in dirs:
-        scan_directory( os.path.join( 'libs', m, dir ), x, gm, deps )
+        scan_directory( os.path.join( 'libs', m, dir ), x, gm, deps, dep_path )
 
 
 def read_exceptions():
@@ -197,7 +202,7 @@ def install_modules( modules, git_args ):
         raise Exception( "The command '%s' failed with exit code %d" % (command, r) )
 
 
-def install_module_dependencies( deps, x, gm, git_args ):
+def install_module_dependencies( deps, x, gm, git_args, dep_path ):
 
     modules = []
 
@@ -214,11 +219,20 @@ def install_module_dependencies( deps, x, gm, git_args ):
     install_modules( modules, git_args )
 
     for m in modules:
-        scan_module_dependencies( m, x, gm, deps, [ 'include', 'src' ] )
+        next_dep_path = dep_path
+
+        if dep_path:
+            next_dep_path = dep_path + [m]
+
+        scan_module_dependencies( m, x, gm, deps, [ 'include', 'src' ], next_dep_path )
 
     return len( modules )
 
 
+class DependencyCycle(Exception):
+    pass
+
+
 if( __name__ == "__main__" ):
 
     parser = argparse.ArgumentParser( description='Installs the dependencies needed to test a Boost library.' )
@@ -230,6 +244,7 @@ def install_module_dependencies( deps, x, gm, git_args ):
     parser.add_argument( '-I', '--include', help="additional subdirectory to scan; can be repeated", metavar='DIR', action='append', default=[] )
     parser.add_argument( '-g', '--git_args', help="additional arguments to `git submodule update`", default='', action='store' )
     parser.add_argument( '-u', '--update', help='update <library> before scanning', action='store_true' )
+    parser.add_argument( '-C', '--reject-cycles', help='abort if <library> has cyclical dependencies', action='store_true' )
     parser.add_argument( 'library', help="name of library to scan ('libs/' will be prepended)" )
 
     args = parser.parse_args()
@@ -239,6 +254,7 @@ def install_module_dependencies( deps, x, gm, git_args ):
     vprint( 2, '-X:', args.exclude )
     vprint( 2, '-I:', args.include )
     vprint( 2, '-N:', args.ignore )
+    vprint( 2, '-C:', args.reject_cycles )
 
     x = read_exceptions()
     vprint( 2, 'Exceptions:', x )
@@ -257,26 +273,57 @@ def install_module_dependencies( deps, x, gm, git_args ):
 
     m = args.library
 
-    deps = { m : 1 }
-
-    dirs = [ 'include', 'src', 'test' ]
+    main_dirs = [ 'include', 'src' ]
+    extra_dirs = [ 'test' ]
 
     for dir in args.exclude:
-      dirs.remove( dir )
+        if dir in main_dirs:
+            main_dirs.remove( dir )
+
+        if dir in extra_dirs:
+            extra_dirs.remove( dir )
 
     for dir in args.include:
-      dirs.append( dir )
+      extra_dirs.append( dir )
 
-    vprint( 1, 'Directories to scan:', *dirs )
+    vprint( 1, 'Directories to scan:', *(main_dirs + extra_dirs) )
 
-    scan_module_dependencies( m, x, gm, deps, dirs )
+    dep_path = []
+    if args.reject_cycles:
+        dep_path.append( m )
+
+    main_deps = { m : 1 }
+    scan_module_dependencies( m, x, gm, main_deps, main_dirs, dep_path )
+
+    extra_deps = { m : 1 }
+    scan_module_dependencies( m, x, gm, extra_deps, extra_dirs, [] )
 
     for dep in args.ignore:
-        if dep in deps:
+        reported = False
+
+        if dep in main_deps:
             vprint( 1, 'Ignoring dependency', dep )
-            del deps[dep]
+            reported = True
+            del main_deps[dep]
+
+        if dep in extra_deps:
+            if not reported:
+                vprint( 1, 'Ignoring dependency', dep )
+                reported = True
+            del extra_deps[dep]
+
+    all_deps = dict( **main_deps )
+    all_deps.update( extra_deps )
+    vprint( 2, 'Dependencies:', all_deps )
+
+    try:
+
+        while install_module_dependencies( main_deps, x, gm, args.git_args, dep_path ):
+            pass
 
-    vprint( 2, 'Dependencies:', deps )
+        while install_module_dependencies( extra_deps, x, gm, args.git_args, [] ):
+            pass
 
-    while install_module_dependencies( deps, x, gm, args.git_args ):
-        pass
+    except DependencyCycle as e:
+        print( e, file=sys.stderr )
+        sys.exit(1)