diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 4943bfc..3e4c963 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -9438,7 +9438,8 @@
 		break;
 #if defined(FEAT_CLIENTSERVER)
 	case SPEC_CLIENT:	/* Source of last submitted input */
-		sprintf((char *)strbuf, "0x%x", (unsigned int)clientWindow);
+		sprintf((char *)strbuf, PRINTF_HEX_LONG_U,
+							(long_u)clientWindow);
 		result = strbuf;
 		break;
 #endif