diff -urN ../exim-4.91.orig/src/malware.c ./src/malware.c
--- ../exim-4.91.orig/src/malware.c	2018-04-15 02:18:10.000000000 +0300
+++ ./src/malware.c	2018-05-01 19:34:50.976641000 +0300
@@ -77,7 +77,7 @@
 
 spf(buf, sizeof(buf), US"_HAVE_MALWARE_");
 
-for (sc = m_scans; sc->scancode != -1; sc++)
+for (sc = m_scans; (int)sc->scancode != -1; sc++)
   {
   for(s = sc->name, t = buf+14; *s; s++) if (*s != '-') *t++ = toupper(*s);
   *t = '\0';
@@ -2245,7 +2245,7 @@
 {
 struct scan * sc;
 fprintf(f, "Malware:");
-for (sc = m_scans; sc->scancode != -1; sc++) fprintf(f, " %s", sc->name);
+for (sc = m_scans; (int)sc->scancode != -1; sc++) fprintf(f, " %s", sc->name);
 fprintf(f, "\n");
 }