diff --git a/compare-for-test/qpdf-test-compare.cc b/compare-for-test/qpdf-test-compare.cc
index 3952381b..5d3e6e28 100644
--- a/compare-for-test/qpdf-test-compare.cc
+++ b/compare-for-test/qpdf-test-compare.cc
@@ -129,12 +129,12 @@ cleanTrailer(QPDFObjectHandle& trailer)
 }
 
 std::string
-compare(char const* actual_filename, char const* expected_filename)
+compare(char const* actual_filename, char const* expected_filename, char const* password)
 {
     QPDF actual;
-    actual.processFile(actual_filename);
+    actual.processFile(actual_filename, password);
     QPDF expected;
-    expected.processFile(expected_filename);
+    expected.processFile(expected_filename, password);
     // The motivation behind this program is to compare files in a way that allows for
     // differences in the exact bytes of zlib compression. If all zlib implementations produced
     // exactly the same output, we would just be able to use straight comparison, but since they
@@ -191,16 +191,20 @@ main(int argc, char* argv[])
         exit(0);
     }
 
-    if (argc != 3) {
+    if (argc < 3 || argc > 4) {
         usage();
     }
 
     bool show_why = QUtil::get_env("QPDF_COMPARE_WHY");
     try {
         char const* to_output;
-        auto actual = argv[1];
-        auto expected = argv[2];
-        auto difference = compare(actual, expected);
+        char const* actual = argv[1];
+        char const* expected = argv[2];
+        char const* password{nullptr};
+        if (argc == 4) {
+            password = argv[3];
+        }
+        auto difference = compare(actual, expected, password);
         if (difference.empty()) {
             // The files are identical; write the expected file. This way, tests can be written
             // that compare the output of this program to the expected file.
diff --git a/compare-for-test/qtest/compare.test b/compare-for-test/qtest/compare.test
index bcf6b788..198cdf6b 100644
--- a/compare-for-test/qtest/compare.test
+++ b/compare-for-test/qtest/compare.test
@@ -73,7 +73,7 @@ foreach my $f (@diff)
 }
 
 # Repeat for encrypted files.
-$n_tests += 3;
+$n_tests += 5;
 $td->runtest("byte-wise compare encrypted files",
              {$td->COMMAND => "cmp enc1.pdf enc2.pdf"},
              {$td->REGEXP => ".*", $td->EXIT_STATUS => "!0"});
@@ -84,6 +84,13 @@ $td->runtest("compare encrypted files (different)",
              {$td->COMMAND => "env QPDF_COMPARE_WHY=1 qpdf-test-compare enc1.pdf diff-data-enc.pdf"},
              {$td->STRING => "4,0: stream data differs\n", $td->EXIT_STATUS => 2},
              $td->NORMALIZE_NEWLINES);
+$td->runtest("with password (same)",
+             {$td->COMMAND => "env QPDF_COMPARE_WHY=1 qpdf-test-compare enc1.pdf enc2.pdf o"},
+             {$td->FILE => "enc2.pdf", $td->EXIT_STATUS => 0});
+$td->runtest("with password (different)",
+             {$td->COMMAND => "env QPDF_COMPARE_WHY=1 qpdf-test-compare enc1.pdf diff-data-enc.pdf o"},
+             {$td->STRING => "4,0: stream data differs\n", $td->EXIT_STATUS => 2},
+             $td->NORMALIZE_NEWLINES);
 
 # Object streams
 $n_tests += 1;