diff --git a/win/X11/tile2x11.c b/win/X11/tile2x11.c
index 2f774065a..97059dd5e 100644
--- a/win/X11/tile2x11.c
+++ b/win/X11/tile2x11.c
@@ -240,3 +240,15 @@ main(int argc, char *argv[])
     fclose(fp);
     return 0;
 }
+
+/* we need a local copy of this for alloc.o and because we don't have panic() */
+unsigned
+FITSuint_(unsigned long long i, const char *file, int line){
+    unsigned ret = (unsigned)i;
+    if (ret != i) {
+        Fprintf(stderr, "Overflow at %s:%d", file, line);
+        exit(1);
+    }
+    return (unsigned)i;
+}
+