diff --git a/changes/bug19682 b/changes/bug19682
new file mode 100644
index 0000000000..c799c417ac
--- /dev/null
+++ b/changes/bug19682
@@ -0,0 +1,3 @@
+  o Minor bugfixes (compilation):
+    - Fix compilation warning in the unit tests on systems where
+      char is signed. Fixes bug 19682; bugfix on 0.2.8.1-alpha.
diff --git a/src/test/test_util_format.c b/src/test/test_util_format.c
index a25054cd0a..3d02930983 100644
--- a/src/test/test_util_format.c
+++ b/src/test/test_util_format.c
@@ -106,10 +106,10 @@ test_util_format_base64_encode(void *ignored)
   for (i = 0;i<50;i++) {
     src[i] = 0;
   }
-  src[50] = 255;
-  src[51] = 255;
-  src[52] = 255;
-  src[53] = 255;
+  src[50] = (char)255;
+  src[51] = (char)255;
+  src[52] = (char)255;
+  src[53] = (char)255;
 
   res = base64_encode(dst, 1000, src, 54, BASE64_ENCODE_MULTILINE);
   tt_int_op(res, OP_EQ, 74);