diff --git a/ext/mbstring/libmbfl/mbfl/mbfl_convert.c b/ext/mbstring/libmbfl/mbfl/mbfl_convert.c
index dda978a71223b..f6e860a35aead 100644
--- a/ext/mbstring/libmbfl/mbfl/mbfl_convert.c
+++ b/ext/mbstring/libmbfl/mbfl/mbfl_convert.c
@@ -307,7 +307,8 @@ const struct mbfl_convert_vtbl* mbfl_convert_filter_get_vtbl(const mbfl_encoding
 		from = &mbfl_encoding_8bit;
 	} else if (from->no_encoding == mbfl_no_encoding_base64 ||
 			   from->no_encoding == mbfl_no_encoding_qprint ||
-			   from->no_encoding == mbfl_no_encoding_uuencode) {
+			   from->no_encoding == mbfl_no_encoding_uuencode ||
+			   from->no_encoding == mbfl_no_encoding_7bit) {
 		to = &mbfl_encoding_8bit;
 	}
 
diff --git a/ext/mbstring/tests/bug81693.phpt b/ext/mbstring/tests/bug81693.phpt
new file mode 100644
index 0000000000000..ae52453f8765d
--- /dev/null
+++ b/ext/mbstring/tests/bug81693.phpt
@@ -0,0 +1,10 @@
+--TEST--
+Bug #81693 (mb_check_encoding(7bit) segfaults)
+--EXTENSIONS--
+mbstring
+--FILE--
+<?php
+var_dump(mb_check_encoding('Hello world', '7bit'));
+?>
+--EXPECT--
+bool(true)