diff --git a/tests/scripts/check-doxy-blocks.pl b/tests/scripts/check-doxy-blocks.pl
index abd27a8..b0fd696 100755
--- a/tests/scripts/check-doxy-blocks.pl
+++ b/tests/scripts/check-doxy-blocks.pl
@@ -19,6 +19,10 @@
 # everything with a backslach except '\0' and backslash at EOL
 my $doxy_re = qr/\\(?!0|\n)/;
 
+# Return an error code to the environment if a potential error in the
+# source code is found.
+my $exit_code = 0;
+
 sub check_file {
     my ($fname) = @_;
     open my $fh, '<', $fname or die "Failed to open '$fname': $!\n";
@@ -32,6 +36,7 @@
         if ($block_start and $line =~ m/$doxy_re/) {
             print "$fname:$block_start: directive on line $.\n";
             $block_start = 0; # report only one directive per block
+            $exit_code = 1;
         }
     }
 
@@ -45,13 +50,15 @@
     }
 }
 
-# locate root directory based on invocation name
-my $root = dirname($0) . '/..';
-chdir $root or die "Can't chdir to '$root': $!\n";
-
-# just do it
+# Check that the script is being run from the project's root directory.
 for my $dir (@directories) {
-    check_dir($dir)
+    if (! -d $dir) {
+        die "This script must be run from the mbed TLS root directory";
+    } else {
+        check_dir($dir)
+    }
 }
 
+exit $exit_code;
+
 __END__