diff --git a/libbb/replace.c b/libbb/replace.c
index a661d96e6..6183d3e6f 100644
--- a/libbb/replace.c
+++ b/libbb/replace.c
@@ -15,6 +15,10 @@ unsigned FAST_FUNC count_strstr(const char *str, const char *sub)
 	size_t sub_len = strlen(sub);
 	unsigned count = 0;
 
+	/* If sub is empty, avoid an infinite loop */
+	if (sub_len == 0)
+		return strlen(str) + 1;
+
 	while ((str = strstr(str, sub)) != NULL) {
 		count++;
 		str += sub_len;