diff --git a/src/libc/pthread/thread.rs b/src/libc/pthread/thread.rs
index 648d6b00a..1a9ee3a51 100644
--- a/src/libc/pthread/thread.rs
+++ b/src/libc/pthread/thread.rs
@@ -110,7 +110,7 @@ pub fn pthread_attr_setstacksize(
     attr: MutPtr<pthread_attr_t>,
     stacksize: GuestUSize,
 ) -> i32 {
-    if attr.is_null() || stacksize < PTHREAD_STACK_MIN || stacksize.is_multiple_of(PAGE_SIZE) {
+    if attr.is_null() || stacksize < PTHREAD_STACK_MIN || !stacksize.is_multiple_of(PAGE_SIZE) {
         return EINVAL;
     }
     check_magic!(env, attr, MAGIC_ATTR);
diff --git a/src/mem/allocator.rs b/src/mem/allocator.rs
index 66304219d..cfb97469e 100644
--- a/src/mem/allocator.rs
+++ b/src/mem/allocator.rs
@@ -334,7 +334,7 @@ impl Allocator {
     }
 
     fn align(size: GuestUSize, align: GuestUSize) -> GuestUSize {
-        if size.is_multiple_of(align) {
+        if !size.is_multiple_of(align) {
             size + align - (size % align)
         } else {
             size