diff --git a/lib/mem/alloc_linux.q b/lib/mem/alloc_linux.q
index df8fe5b..2389b04 100644
--- a/lib/mem/alloc_linux.q
+++ b/lib/mem/alloc_linux.q
@@ -3,7 +3,7 @@ import sys
 alloc(length Int) -> Pointer {
 	x := sys.mmap(0, length+8, 0x1|0x2, 0x02|0x20)
 
-	if x <= 0 {
+	if x < 0x1000 {
 		return x
 	}
 
diff --git a/lib/mem/alloc_mac.q b/lib/mem/alloc_mac.q
index 42da24b..6ffda84 100644
--- a/lib/mem/alloc_mac.q
+++ b/lib/mem/alloc_mac.q
@@ -1,9 +1,9 @@
 import sys
 
 alloc(length Int) -> Pointer {
-	x := sys.mmap(0, length, 0x1|0x2, 0x02|0x1000)
+	x := sys.mmap(0, length+8, 0x1|0x2, 0x02|0x1000)
 
-	if x <= 0 {
+	if x < 0x1000 {
 		return x
 	}
 
diff --git a/lib/mem/alloc_windows.q b/lib/mem/alloc_windows.q
index 616fb84..d448dd0 100644
--- a/lib/mem/alloc_windows.q
+++ b/lib/mem/alloc_windows.q
@@ -1,9 +1,9 @@
 import sys
 
 alloc(length Int) -> Pointer {
-	x := sys.mmap(0, length, 0x0004, 0x3000)
+	x := sys.mmap(0, length+8, 0x0004, 0x3000)
 
-	if x <= 0 {
+	if x < 0x1000 {
 		return x
 	}