diff --git a/src/io/conf.c b/src/io/conf.c
index 517fe03..8a9515c 100644
--- a/src/io/conf.c
+++ b/src/io/conf.c
@@ -17,7 +17,7 @@
 static const char *strmat(const char *s1, const char *s2) PURE NONNULL((1, 2));
 static const char *strmat(const char *s1, const char *s2)
 {
-	while ((*s1 == *s2) & !!*s1)
+	while ((*s1 == *s2) && *s1)
 		s1++, s2++;
 	return s1;
 }