diff --git a/wkd-java/src/main/java/pgp/wkd/discovery/WKDPolicy.java b/wkd-java/src/main/java/pgp/wkd/discovery/WKDPolicy.java
index 763a24e..5007d5d 100644
--- a/wkd-java/src/main/java/pgp/wkd/discovery/WKDPolicy.java
+++ b/wkd-java/src/main/java/pgp/wkd/discovery/WKDPolicy.java
@@ -32,6 +32,15 @@ public final class WKDPolicy {
         this.submissionAddress = submissionAddress;
     }
 
+    /**
+     * Parse a {@link WKDPolicy} object by reading from the given {@link InputStream}.
+     * The stream will be closed by this method.
+     *
+     * @param inputStream InputStream
+     * @return parsed WKDPolicy object
+     *
+     * @throws IOException in case of an error
+     */
     public static WKDPolicy fromInputStream(InputStream inputStream) throws IOException {
         BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
 
@@ -57,7 +66,11 @@ public final class WKDPolicy {
                 continue;
             }
             if (prepared.startsWith(KEYWORD_PROTOCOL_VERSION + ": ")) {
-                protocolVersion = Integer.parseInt(prepared.substring(KEYWORD_PROTOCOL_VERSION.length() + 2));
+                try {
+                    protocolVersion = Integer.parseInt(prepared.substring(KEYWORD_PROTOCOL_VERSION.length() + 2));
+                } catch (NumberFormatException e) {
+                    // ignore
+                }
                 continue;
             }
             if (prepared.startsWith(KEYWORD_SUBMISSION_ADDRESS + ": ")) {
@@ -65,6 +78,8 @@ public final class WKDPolicy {
             }
         }
 
+        inputStream.close();
+
         return new WKDPolicy(mailboxOnly, daneOnly, authSubmit, protocolVersion, submissionAddress);
     }
 
diff --git a/wkd-java/src/test/java/pgp/wkd/WKDPolicyTest.java b/wkd-java/src/test/java/pgp/wkd/WKDPolicyTest.java
index 94d63c9..9d43794 100644
--- a/wkd-java/src/test/java/pgp/wkd/WKDPolicyTest.java
+++ b/wkd-java/src/test/java/pgp/wkd/WKDPolicyTest.java
@@ -30,6 +30,23 @@ public class WKDPolicyTest {
         assertNull(policy.getSubmissionAddress());
     }
 
+    @Test
+    public void parseWhitespaceOnlyPolicy() throws IOException {
+        ByteArrayInputStream whitespaceOnly = new ByteArrayInputStream(
+                ("\n" +
+                        "\r\n" +
+                        "     \n" +
+                        "\t\n" +
+                        "\n").getBytes(StandardCharsets.UTF_8));
+        WKDPolicy policy = WKDPolicy.fromInputStream(whitespaceOnly);
+
+        assertFalse(policy.isMailboxOnly());
+        assertFalse(policy.isDaneOnly());
+        assertFalse(policy.isAuthSubmit());
+        assertNull(policy.getProtocolVersion());
+        assertNull(policy.getSubmissionAddress());
+    }
+
     @Test
     public void parseSparsePolicy() throws IOException {
         ByteArrayInputStream sparse = new ByteArrayInputStream(
@@ -51,7 +68,7 @@ public class WKDPolicyTest {
                         "auth-submit\n" +
                         "protocol-version: 12\n" +
                         "submission-address: key-submission-example.org@directory.example.org")
-                                .getBytes(StandardCharsets.UTF_8));
+                        .getBytes(StandardCharsets.UTF_8));
         WKDPolicy policy = WKDPolicy.fromInputStream(full);
 
         assertTrue(policy.isMailboxOnly());
@@ -61,4 +78,33 @@ public class WKDPolicyTest {
         assertEquals(12, policy.getProtocolVersion());
         assertEquals("key-submission-example.org@directory.example.org", policy.getSubmissionAddress());
     }
+
+    @Test
+    public void malformedInput_MissingSpaces() throws IOException {
+        ByteArrayInputStream malformed = new ByteArrayInputStream(
+                ("submission-address submit-keys-here@directory.example.org\n" +
+                        "protocol-version:12").getBytes(StandardCharsets.UTF_8));
+
+        WKDPolicy policy = WKDPolicy.fromInputStream(malformed);
+        assertNull(policy.getProtocolVersion());
+    }
+
+    @Test
+    public void malformedInput_missingColon() throws IOException {
+        ByteArrayInputStream malformed = new ByteArrayInputStream(
+                ("submission-address submit-keys-here@directory.example.org\n" +
+                        "protocol-version 13").getBytes(StandardCharsets.UTF_8));
+        WKDPolicy policy = WKDPolicy.fromInputStream(malformed);
+        assertNull(policy.getSubmissionAddress());
+        assertNull(policy.getProtocolVersion());
+    }
+
+    @Test
+    public void malformedInput_NotANumber() throws IOException {
+        ByteArrayInputStream malformed = new ByteArrayInputStream(
+                "protocol-version: ABC".getBytes(StandardCharsets.UTF_8));
+
+        WKDPolicy policy = WKDPolicy.fromInputStream(malformed);
+        assertNull(policy.getProtocolVersion());
+    }
 }