diff --git a/api/syscalls.json b/api/syscalls.json
index 11b769a..7f392b3 100644
--- a/api/syscalls.json
+++ b/api/syscalls.json
@@ -95,12 +95,12 @@
           ]
         ],
         "returns": [
-          "bool",
-          "success"
+          "u64",
+          "new_size"
         ],
         "permission": "default_allowed",
         "const_idx": 17,
-        "description": "Resize the heap to a new size given in bytes. This is similar to the `brk()` system call on POSIX systems. Note that the heap may be resized to a size larger than requested. The heap size is guaranteed to be a multiple of at least 8 bytes. Returns the new heap size in bytes if successful, or `UINT64_MAX` on failure."
+        "description": "Resize the heap to a new size given in bytes. This is similar to the `brk()` system call on POSIX systems. Note that the heap may be resized to a size larger than requested. The heap size is guaranteed to be a multiple of 8 bytes. Returns the new heap size in bytes if successful, or `UINT64_MAX` on failure."
       }
     ],
     "constants": []
diff --git a/doc/syscalls.md b/doc/syscalls.md
index 29af29d..d8c4ea9 100644
--- a/doc/syscalls.md
+++ b/doc/syscalls.md
@@ -51,12 +51,12 @@ Report the current heap size in bytes.
 ## vm_resize_heap
 
 ```
-bool vm_resize_heap(u64 num_bytes)
+u64 vm_resize_heap(u64 num_bytes)
 ```
 
-**Returns:** `bool success`
+**Returns:** `u64 new_size`
 
-Resize the heap to a new size given in bytes. This is similar to the `brk()` system call on POSIX systems. Note that the heap may be resized to a size larger than requested. The heap size is guaranteed to be a multiple of at least 8 bytes. Returns the new heap size in bytes if successful, or `UINT64_MAX` on failure.
+Resize the heap to a new size given in bytes. This is similar to the `brk()` system call on POSIX systems. Note that the heap may be resized to a size larger than requested. The heap size is guaranteed to be a multiple of 8 bytes. Returns the new heap size in bytes if successful, or `UINT64_MAX` on failure.
 
 # io
 
diff --git a/ncc/include/uvm/syscalls.h b/ncc/include/uvm/syscalls.h
index 3268a37..2af7c02 100644
--- a/ncc/include/uvm/syscalls.h
+++ b/ncc/include/uvm/syscalls.h
@@ -21,9 +21,9 @@
 // Report the current heap size in bytes.
 #define vm_heap_size() asm () -> u64 { syscall vm_heap_size; }
 
-// bool vm_resize_heap(u64 num_bytes)
-// Resize the heap to a new size given in bytes. This is similar to the `brk()` system call on POSIX systems. Note that the heap may be resized to a size larger than requested. The heap size is guaranteed to be a multiple of at least 8 bytes. Returns the new heap size in bytes if successful, or `UINT64_MAX` on failure.
-#define vm_resize_heap(__num_bytes) asm (__num_bytes) -> bool { syscall vm_resize_heap; }
+// u64 vm_resize_heap(u64 num_bytes)
+// Resize the heap to a new size given in bytes. This is similar to the `brk()` system call on POSIX systems. Note that the heap may be resized to a size larger than requested. The heap size is guaranteed to be a multiple of 8 bytes. Returns the new heap size in bytes if successful, or `UINT64_MAX` on failure.
+#define vm_resize_heap(__num_bytes) asm (__num_bytes) -> u64 { syscall vm_resize_heap; }
 
 // void print_i64(i64 val)
 // Print an i64 value to standard output.