diff --git a/event.c b/event.c
index 176cc880..6d66f931 100644
--- a/event.c
+++ b/event.c
@@ -67,6 +67,7 @@
 #include "iocp-internal.h"
 #include "changelist-internal.h"
 #include "ht-internal.h"
+#include "util-internal.h"
 
 #ifdef _EVENT_HAVE_EVENT_PORTS
 extern const struct eventop evportops;
@@ -446,7 +447,7 @@ event_is_method_disabled(const char *name)
 
 	evutil_snprintf(environment, sizeof(environment), "EVENT_NO%s", name);
 	for (i = 8; environment[i] != '\0'; ++i)
-		environment[i] = toupper(environment[i]);
+		environment[i] = EVUTIL_TOUPPER(environment[i]);
 	/* Note that evutil_getenv() ignores the environment entirely if
 	 * we're setuid */
 	return (evutil_getenv(environment) != NULL);
diff --git a/test/regress.c b/test/regress.c
index dacda068..82c7c3b6 100644
--- a/test/regress.c
+++ b/test/regress.c
@@ -1875,7 +1875,7 @@ methodname_to_envvar(const char *mname, char *buf, size_t buflen)
 	char *cp;
 	evutil_snprintf(buf, buflen, "EVENT_NO%s", mname);
 	for (cp = buf; *cp; ++cp) {
-		*cp = toupper(*cp);
+		*cp = EVUTIL_TOUPPER(*cp);
 	}
 }
 #endif