diff --git a/ext/standard/filters.c b/ext/standard/filters.c
index 0a59039635881..15dae1bee69d7 100644
--- a/ext/standard/filters.c
+++ b/ext/standard/filters.c
@@ -951,7 +951,9 @@ static php_conv_err_t php_conv_qprint_encode_convert(php_conv_qprint_encode *ins
 			*(pd++) = qp_digits[(c & 0x0f)];
 			ocnt -= 3;
 			line_ccnt -= 3;
-			trail_ws--;
+			if (trail_ws > 0) {
+				trail_ws--;
+			}
 			CONSUME_CHAR(ps, icnt, lb_ptr, lb_cnt);
 		}
 	}
diff --git a/ext/standard/tests/streams/bug65483.phpt b/ext/standard/tests/streams/bug65483.phpt
new file mode 100644
index 0000000000000..d214bbbbcc4a4
--- /dev/null
+++ b/ext/standard/tests/streams/bug65483.phpt
@@ -0,0 +1,19 @@
+--TEST--
+Bug #65483: quoted-printable encode stream filter incorrectly encoding spaces
+--FILE--
+<?php
+
+$data = 'a b=c d';
+
+$fd = fopen('php://temp', 'w+');
+fwrite($fd, $data);
+rewind($fd);
+
+$res = stream_filter_append($fd, 'convert.quoted-printable-encode', STREAM_FILTER_READ);
+var_dump(stream_get_contents($fd, -1, 0));
+
+fclose($fd);
+
+?>
+--EXPECT--
+string(9) "a b=3Dc d"