diff --git a/ext/standard/tests/streams/gh15980.phpt b/ext/standard/tests/streams/gh15980.phpt
new file mode 100644
index 0000000000000..7a9d8364a90ae
--- /dev/null
+++ b/ext/standard/tests/streams/gh15980.phpt
@@ -0,0 +1,12 @@
+--TEST--
+GH-15980 (Signed integer overflow in main/streams/streams.c)
+--FILE--
+<?php
+$s = fopen(__FILE__, "r");
+fseek($s, 1);
+$seekres = fseek($s, PHP_INT_MAX, SEEK_CUR);
+$tellres = ftell($s);
+var_dump($seekres === -1 || $tellres > 1);
+?>
+--EXPECT--
+bool(true)
diff --git a/main/streams/streams.c b/main/streams/streams.c
index e22d9e51d594a..4c66d8aadc39b 100644
--- a/main/streams/streams.c
+++ b/main/streams/streams.c
@@ -1354,8 +1354,13 @@ PHPAPI int _php_stream_seek(php_stream *stream, zend_off_t offset, int whence)
 
 		switch(whence) {
 			case SEEK_CUR:
-				offset = stream->position + offset;
-				whence = SEEK_SET;
+				ZEND_ASSERT(stream->position >= 0);
+				if (UNEXPECTED(offset > ZEND_LONG_MAX - stream->position)) {
+					offset = ZEND_LONG_MAX;
+				} else {
+					offset = stream->position + offset;
+				}
+ 				whence = SEEK_SET;
 				break;
 		}
 		ret = stream->ops->seek(stream, offset, whence, &stream->position);