diff --git a/ChangeLog.d/fix_memsan_build_clang11.txt b/ChangeLog.d/fix_memsan_build_clang11.txt
new file mode 100644
index 000000000..3f5cc058f
--- /dev/null
+++ b/ChangeLog.d/fix_memsan_build_clang11.txt
@@ -0,0 +1,2 @@
+Changes
+   * Fix memsan build false positive in x509_crt.c with clang 11
diff --git a/library/x509_crt.c b/library/x509_crt.c
index a623c57a6..0aa4f4c21 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1629,6 +1629,8 @@ cleanup:
     }
 #endif /* MBEDTLS_THREADING_C */
 
+    memset( &sb, 0, sizeof( sb ) );
+
     while( ( entry = readdir( dir ) ) != NULL )
     {
         snp_ret = mbedtls_snprintf( entry_name, sizeof entry_name,