diff --git a/checkmk/custom-files/local/monitor-certificates b/checkmk/custom-files/local/monitor-certificates
index 03f41482811defa5e40b98db83c08c4d9ad4c8fa..2e82f746903756d059bdfbcae42bc0f4af6453c6 100644
--- a/checkmk/custom-files/local/monitor-certificates
+++ b/checkmk/custom-files/local/monitor-certificates
@@ -20,7 +20,7 @@ function process_folder {
     fi
     pemfiles=$(find "$folder" -type f -name '*.pem')
     for pemfile in $pemfiles; do
-        if [[ "$pemfile" =~ \.(dhparam|fullchain|chain|cacert)\.pem$ ]]; then
+        if [[ "$pemfile" =~ \.(dhparam|fullchain|chain|cacert|key)\.pem$ ]]; then
             continue;
         fi
         pem_subject=$(openssl x509 -in "$pemfile" -noout -text 2>&1 | grep 'Subject:' | tr -s ' ' | cut -d ' ' -f 3-)