diff --git a/ChangeLog b/ChangeLog
index 7d2e134a81..75f3be9341 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Jun  8 22:22:24 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
+
+	* string.c: Revert previous commit (possibility of endless loop).
+
 Wed Jun  8 21:57:41 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
 
 	* string.c: Special-case :ascii option in rb_str_upcase_bang.
diff --git a/string.c b/string.c
index a8d06be52d..e1cedf42aa 100644
--- a/string.c
+++ b/string.c
@@ -5871,6 +5871,7 @@ static VALUE
 rb_str_upcase_bang(int argc, VALUE *argv, VALUE str)
 {
     rb_encoding *enc;
+    int modify = 0;
     OnigCaseFoldType flags = ONIGENC_CASE_UPCASE;
 
     flags = check_case_options(argc, argv, flags);
@@ -5886,17 +5887,17 @@ rb_str_upcase_bang(int argc, VALUE *argv, VALUE str)
 
 	    if (rb_enc_isascii(c, enc) && 'a' <= c && c <= 'z') {
 		*s = 'A' + (c - 'a');
-		flags |= ONIGENC_CASE_MODIFIED;
+		modify = 1;
 	    }
 	    s++;
 	}
     }
-    else if (flags&ONIGENC_CASE_ASCII_ONLY)
-        rb_str_ascii_casemap(str, &flags, enc);
-    else
+    else {
 	str_shared_replace(str, rb_str_casemap(str, &flags, enc));
+	modify = ONIGENC_CASE_MODIFIED & flags;
+    }
 
-    if (ONIGENC_CASE_MODIFIED&flags) return str;
+    if (modify) return str;
     return Qnil;
 }