diff --git a/lib/mem/alloc.q b/lib/mem/alloc.q
index 138f871..af6ab70 100644
--- a/lib/mem/alloc.q
+++ b/lib/mem/alloc.q
@@ -3,9 +3,10 @@ alloc(length uint) -> (buffer ![]byte) {
 
 	if heap.current + aligned > heap.max {
 		size := (heap.max - heap.min + 32) * 2 as uint
+		needed := (aligned + 32 + (pageSize - 1)) & -pageSize
 
-		if size < pageSize {
-			size = (aligned + (pageSize - 1)) & -pageSize
+		if size < needed {
+			size = needed
 		}
 
 		x := rawAlloc(size)
diff --git a/tests/memory-growth.q b/tests/memory-growth.q
new file mode 100644
index 0000000..7edeb8b
--- /dev/null
+++ b/tests/memory-growth.q
@@ -0,0 +1,7 @@
+import mem
+
+main() {
+	_ := new(byte, 1)
+	b := new(byte, 20000000)
+	assert mem.heap.max - b.ptr >= b.len
+}
\ No newline at end of file
diff --git a/tests/tests_test.go b/tests/tests_test.go
index b165049..e2e756d 100644
--- a/tests/tests_test.go
+++ b/tests/tests_test.go
@@ -100,6 +100,7 @@ var tests = []run{
 	{"fibonacci", nil, "", "", 0},
 	{"memory", nil, "", "Hello\n", 0},
 	{"out-of-memory", nil, "", "(x as int) >= 0x1000\n", 1},
+	{"memory-growth", nil, "", "", 0},
 	{"index-static", nil, "", "", 0},
 	{"index-dynamic", nil, "", "", 0},
 	{"struct", nil, "", "", 0},