diff --git a/avr/modules/heap/main.asm b/avr/modules/heap/main.asm
index edf8028..fa9fadd 100644
--- a/avr/modules/heap/main.asm
+++ b/avr/modules/heap/main.asm
@@ -78,6 +78,7 @@ Heap_Init:
 ; @param r25:r24 number of bytes to alloc
 ; @return CFLAG set of okay, cleared otherwise
 ; @return X start of allocated memory
+; @clobbers r16, r17, r18, r19, r24, r25, X
 
 Heap_Alloc:
   rjmp heapAllocFirstFit
@@ -92,6 +93,7 @@ Heap_Alloc:
 ; @param r25:r24 number of bytes to alloc
 ; @return CFLAG set of okay, cleared otherwise
 ; @return X start of allocated memory
+; @clobbers r16, r17, r18, r19, r24, r25, X
 
 heapAllocFirstFit:
   adiw r25:r24, 3 ; align size to next multiple of 4
@@ -109,7 +111,7 @@ heapAllocFirstFit_loop:
     sbrc r18, HEAP_HEADER_BIT_USED
       rjmp heapAllocFirstFit_next ; jump if used
     ; current chunk free, check size
-	andi r18, 0xfc
+    andi r18, 0xfc
     mov r16, r18
     mov r17, r19
     sub r16, r24
@@ -119,7 +121,7 @@ heapAllocFirstFit_loop:
     sec
     ret
 heapAllocFirstFit_next:
-	andi r18, 0xfc
+    andi r18, 0xfc
     add xl, r18
     adc xh, r19
     adiw xh:xl, 2 ; skip footer