diff --git a/src/libCom/test/epicsStringTest.c b/src/libCom/test/epicsStringTest.c
index ec47f02a3..ce04862e6 100644
--- a/src/libCom/test/epicsStringTest.c
+++ b/src/libCom/test/epicsStringTest.c
@@ -33,8 +33,8 @@ void testChars(void) {
         t = epicsStrnRawFromEscaped(result, sizeof(result), escaped, s);
         testOk(needed == s && t == 1 &&
             result[0] == input[0] && result[1] == 0,
-            "escaped char 0x%2.2x -> \"%s\" (%Zd) -> 0x%2.2x",
-            input[0] & 0xff, escaped, needed, result[0] & 0xff);
+            "escaped char 0x%2.2x -> \"%s\" (%d) -> 0x%2.2x",
+            input[0] & 0xff, escaped, (int) needed, result[0] & 0xff);
     }
 }