diff --git a/sonar-project.properties b/sonar-project.properties
index dc74b9bd0..287b7eb9c 100644
--- a/sonar-project.properties
+++ b/sonar-project.properties
@@ -1,2 +1,10 @@
 sonar.projectKey=storytold_vectorcraft
 sonar.organization=storytold
+
+# S4790 (weak hash): MD5 is the key derivation of the PDF standard security handler revisions 2-4
+# (ISO 32000-1 §7.6.3.3), which PDF 1.3-1.6 files use. It is needed to read those files and to write
+# the compatibility the user picks, not chosen for new security: the default is 256-bit AES
+# (revision 6), which hashes with SHA-2.
+sonar.issue.ignore.multicriteria=pdf_md5
+sonar.issue.ignore.multicriteria.pdf_md5.ruleKey=rust:S4790
+sonar.issue.ignore.multicriteria.pdf_md5.resourceKey=crates/pdf/src/encrypt.rs