diff --git a/changes/bug23568 b/changes/bug23568
new file mode 100644
index 000000000..cac465568
--- /dev/null
+++ b/changes/bug23568
@@ -0,0 +1,4 @@
+  o Minor bugfixes (compilation):
+    - Fix a compilation warning when building with zstd support
+      on 32-bit platforms. Fixes bug 23568; bugfix on 0.3.1.1-alpha.
+      Found and fixed by Andreas Stieger.
diff --git a/src/common/compress_zstd.c b/src/common/compress_zstd.c
index 0808bcd9a..63e92ed22 100644
--- a/src/common/compress_zstd.c
+++ b/src/common/compress_zstd.c
@@ -62,10 +62,10 @@ tor_zstd_get_version_str(void)
 
   version_number = ZSTD_versionNumber();
   tor_snprintf(version_str, sizeof(version_str),
-               "%lu.%lu.%lu",
-               version_number / 10000 % 100,
-               version_number / 100 % 100,
-               version_number % 100);
+               "%d.%d.%d",
+               (int) version_number / 10000 % 100,
+               (int) version_number / 100 % 100,
+               (int) version_number % 100);
 
   return version_str;
 #else