diff --git a/Zend/tests/zend_alloc_zero_size.phpt b/Zend/tests/zend_alloc_zero_size.phpt
new file mode 100644
index 000000000000..6708ff31c7a3
--- /dev/null
+++ b/Zend/tests/zend_alloc_zero_size.phpt
@@ -0,0 +1,15 @@
+--TEST--
+Zero-size allocations with the tracked allocator
+--EXTENSIONS--
+zend_test
+--ENV--
+USE_ZEND_ALLOC=0
+USE_TRACKED_ALLOC=1
+--FILE--
+<?php
+var_dump(pack(""));
+var_dump(vsprintf("", []));
+?>
+--EXPECT--
+string(0) ""
+string(0) ""
diff --git a/Zend/zend_alloc.c b/Zend/zend_alloc.c
index 3cbdd1e5f5dd..9bfa64bf2123 100644
--- a/Zend/zend_alloc.c
+++ b/Zend/zend_alloc.c
@@ -3291,6 +3291,10 @@ static zend_always_inline zend_result tracked_check_max_allocs(zend_mm_heap *hea
 static void *tracked_malloc(size_t size ZEND_FILE_LINE_DC ZEND_FILE_LINE_ORIG_DC)
 {
 	zend_mm_heap *heap = AG(mm_heap);
+
+	/* malloc(0) may return NULL, so allocate at least one byte. */
+	size = MAX(size, 1);
+
 	if (UNEXPECTED(tracked_check_limit(heap, size ZEND_FILE_LINE_CC) == FAILURE)) {
 		return NULL;
 	}