diff --git a/lib/std/atomic.c3 b/lib/std/atomic.c3
index 0a3a7cc82..f47d8ea4e 100644
--- a/lib/std/atomic.c3
+++ b/lib/std/atomic.c3
@@ -129,13 +129,15 @@ macro @atomic_exec(#func, data, value, ordering) @local
 }
 
 module std::atomic;
+import std::math;
 
 /**
  * @param [&in] ptr "the variable or dereferenced pointer to the data."
  * @param [in] y "the value to be added to ptr."
  * @param $ordering "atomic ordering of the load, defaults to SEQ_CONSISTENT"
  * @return "returns the old value of ptr"
- * 
+ *
+ * @require !$alignment || math::is_power_of_2($alignment) "Alignment must be a power of two."
  * @require types::is_int($typeof(*ptr)) || types::is_float($typeof(*ptr)) "Only integer/float pointers may be used."
  * @require $ordering != AtomicOrdering.NOT_ATOMIC && $ordering != AtomicOrdering.UNORDERED "Acquire ordering is not valid."
  **/
@@ -153,6 +155,7 @@ macro fetch_add(ptr, y, AtomicOrdering $ordering = SEQ_CONSISTENT, bool $volatil
  * @param $ordering "atomic ordering of the load, defaults to SEQ_CONSISTENT"
  * @return "returns the old value of ptr"
  * 
+ * @require !$alignment || math::is_power_of_2($alignment) "Alignment must be a power of two."
  * @require types::is_int($typeof(*ptr)) || types::is_float($typeof(*ptr)) "Only integer/float pointers may be used."
  * @require $ordering != AtomicOrdering.NOT_ATOMIC && $ordering != AtomicOrdering.UNORDERED "Acquire ordering is not valid."
  **/
@@ -170,8 +173,8 @@ macro fetch_sub(ptr, y, AtomicOrdering $ordering = SEQ_CONSISTENT, bool $volatil
  * @param $ordering "atomic ordering of the load, defaults to SEQ_CONSISTENT"
  * @return "returns the old value of ptr"
  * 
-* @require types::is_int($typeof(*ptr)) || types::is_float($typeof(*ptr)) "Only integer/float pointers may be used."
-* @require $ordering != AtomicOrdering.NOT_ATOMIC && $ordering != AtomicOrdering.UNORDERED "Acquire ordering is not valid."
+ * @require types::is_int($typeof(*ptr)) || types::is_float($typeof(*ptr)) "Only integer/float pointers may be used."
+ * @require $ordering != AtomicOrdering.NOT_ATOMIC && $ordering != AtomicOrdering.UNORDERED "Acquire ordering is not valid."
  **/
 macro fetch_mul(ptr, y, AtomicOrdering $ordering = SEQ_CONSISTENT)
 {
@@ -243,6 +246,7 @@ macro fetch_div(ptr, y, AtomicOrdering $ordering = SEQ_CONSISTENT)
  * @param $ordering "atomic ordering of the load, defaults to SEQ_CONSISTENT"
  * @return "returns the old value of ptr"
  * 
+ * @require !$alignment || math::is_power_of_2($alignment) "Alignment must be a power of two."
  * @require types::is_int($typeof(*ptr)) "Only intege pointers may be used."
  * @require types::is_int($typeof(y)) "The value for or must be an int"
  * @require $ordering != AtomicOrdering.NOT_ATOMIC && $ordering != AtomicOrdering.UNORDERED "Acquire ordering is not valid."
@@ -285,6 +289,7 @@ macro fetch_or(ptr, y, AtomicOrdering $ordering = SEQ_CONSISTENT, bool $volatile
  * @param $ordering "atomic ordering of the load, defaults to SEQ_CONSISTENT"
  * @return "returns the old value of ptr"
  * 
+ * @require !$alignment || math::is_power_of_2($alignment) "Alignment must be a power of two."
  * @require types::is_int($typeof(*ptr)) "Only integer pointers may be used."
  * @require types::is_int($typeof(y)) "The value for or must be an int"
  * @require $ordering != AtomicOrdering.NOT_ATOMIC && $ordering != AtomicOrdering.UNORDERED "Acquire ordering is not valid."
@@ -327,6 +332,7 @@ macro fetch_xor(ptr, y, AtomicOrdering $ordering = SEQ_CONSISTENT, bool $volatil
  * @param $ordering "atomic ordering of the load, defaults to SEQ_CONSISTENT"
  * @return "returns the old value of ptr"
  * 
+ * @require !$alignment || math::is_power_of_2($alignment) "Alignment must be a power of two."
  * @require types::is_int($typeof(*ptr)) "Only integer pointers may be used."
  * @require types::is_int($typeof(y)) "The value for or must be an int"
  * @require $ordering != AtomicOrdering.NOT_ATOMIC && $ordering != AtomicOrdering.UNORDERED "Acquire ordering is not valid."
diff --git a/src/compiler/llvm_codegen_builtins.c b/src/compiler/llvm_codegen_builtins.c
index 5c1e94889..3539f0873 100644
--- a/src/compiler/llvm_codegen_builtins.c
+++ b/src/compiler/llvm_codegen_builtins.c
@@ -112,6 +112,7 @@ INLINE void llvm_emit_compare_exchange(GenContext *c, BEValue *result_value, Exp
 												 ordering_to_llvm(success_ordering), ordering_to_llvm(failure_ordering), false);
 	if (alignment && alignment >= type_abi_alignment(type))
 	{
+		assert(is_power_of_two(alignment));
 		LLVMSetAlignment(result, alignment);
 	}
 	if (is_volatile)
@@ -232,9 +233,10 @@ INLINE void llvm_emit_atomic_fetch(GenContext *c, BuiltinFunction func, BEValue
 	                   llvm_atomic_ordering(expr->call_expr.arguments[3]->const_expr.ixx.i.low),
 					   false);
 	if (expr->call_expr.arguments[2]->const_expr.b) LLVMSetVolatile(res, true);
-	uint64_t alignment = expr->call_expr.arguments[3]->const_expr.ixx.i.low;
+	uint64_t alignment = expr->call_expr.arguments[4]->const_expr.ixx.i.low;
 	if (alignment)
 	{
+		assert(is_power_of_two(alignment));
 		LLVMSetAlignment(res, alignment);
 	}
 	llvm_value_set(result_value, res, result_value->type);
diff --git a/src/version.h b/src/version.h
index 196268cc2..19bb80370 100644
--- a/src/version.h
+++ b/src/version.h
@@ -1 +1 @@
-#define COMPILER_VERSION "0.4.650"
\ No newline at end of file
+#define COMPILER_VERSION "0.4.651"
\ No newline at end of file