diff --git a/Zend/zend_alloc.c b/Zend/zend_alloc.c
index 3744a83c84e..3a43027346d 100644
--- a/Zend/zend_alloc.c
+++ b/Zend/zend_alloc.c
@@ -980,7 +980,7 @@ get_chunk:
 				heap->cached_chunks = chunk->next;
 			} else {
 #if ZEND_MM_LIMIT
-				if (UNEXPECTED(heap->real_size + ZEND_MM_CHUNK_SIZE > heap->limit)) {
+				if (UNEXPECTED(ZEND_MM_CHUNK_SIZE > heap->limit - heap->real_size)) {
 					if (zend_mm_gc(heap)) {
 						goto get_chunk;
 					} else if (heap->overflow == 0) {
@@ -1484,8 +1484,8 @@ static void *zend_mm_realloc_heap(zend_mm_heap *heap, void *ptr, size_t size, si
 				}
 			} else /* if (new_size > old_size) */ {
 #if ZEND_MM_LIMIT
-				if (UNEXPECTED(heap->real_size + (new_size - old_size) > heap->limit)) {
-					if (zend_mm_gc(heap) && heap->real_size + (new_size - old_size) <= heap->limit) {
+				if (UNEXPECTED(new_size - old_size > heap->limit - heap->real_size)) {
+					if (zend_mm_gc(heap) && new_size - old_size <= heap->limit - heap->real_size) {
 						/* pass */
 					} else if (heap->overflow == 0) {
 #if ZEND_DEBUG
@@ -1730,8 +1730,8 @@ static void *zend_mm_alloc_huge(zend_mm_heap *heap, size_t size ZEND_FILE_LINE_D
 	void *ptr;
 
 #if ZEND_MM_LIMIT
-	if (UNEXPECTED(heap->real_size + new_size > heap->limit)) {
-		if (zend_mm_gc(heap) && heap->real_size + new_size <= heap->limit) {
+	if (UNEXPECTED(new_size > heap->limit - heap->real_size)) {
+		if (zend_mm_gc(heap) && new_size <= heap->limit - heap->real_size) {
 			/* pass */
 		} else if (heap->overflow == 0) {
 #if ZEND_DEBUG
diff --git a/ext/standard/tests/strings/wordwrap_memory_limit.phpt b/ext/standard/tests/strings/wordwrap_memory_limit.phpt
new file mode 100644
index 00000000000..fb0cc5c3bc6
--- /dev/null
+++ b/ext/standard/tests/strings/wordwrap_memory_limit.phpt
@@ -0,0 +1,18 @@
+--TEST--
+No overflow should occur during the memory_limit check for wordwrap()
+--SKIPIF--
+<?php
+if (getenv("USE_ZEND_ALLOC") === "0") die("skip Zend MM disabled");
+?>
+--INI--
+memory_limit=128M
+--FILE--
+<?php
+
+$str = str_repeat('x', 65534);
+$str2 = str_repeat('x', 65535);
+wordwrap($str, 1, $str2);
+
+?>
+--EXPECTF--
+Fatal error: Allowed memory size of 134217728 bytes exhausted%s(tried to allocate %d bytes) in %s on line %d