diff --git a/.github/workflows/sonarcloud.yml b/.github/workflows/sonarcloud.yml
index e78fe1ea3..285fd642f 100644
--- a/.github/workflows/sonarcloud.yml
+++ b/.github/workflows/sonarcloud.yml
@@ -18,4 +18,7 @@ jobs:
   sonarcloud:
     # Tracked at @main so org-wide CI improvements propagate without PR churn.
     uses: storytold/craft-common-actions/.github/workflows/sonarcloud.yml@main
+    with:
+      # Keep coverage tests on the same reviewed, immutable font set as the main gate.
+      fonts-ref: 37827adc41fd165f9a9234ac40f94dbad353aa69
     secrets: inherit
diff --git a/crates/pptx/src/opc.rs b/crates/pptx/src/opc.rs
index a567330b5..807443b91 100644
--- a/crates/pptx/src/opc.rs
+++ b/crates/pptx/src/opc.rs
@@ -251,7 +251,7 @@ pub fn sidecar_part(name: &str) -> bool {
     let file = segs.last().copied().unwrap_or("");
     let stem = file.strip_prefix("chart").unwrap_or("");
     let num = stem.strip_suffix(".xml.rels").or_else(|| stem.strip_suffix(".xml")).unwrap_or("");
-    stem == file || num.is_empty() || !num.chars().all(|c| c.is_ascii_digit())
+    !(stem != file && !num.is_empty() && num.chars().all(|c| c.is_ascii_digit()))
 }
 
 pub fn dir_of(part: &str) -> String {