diff --git a/mm/mm_heap/mm.h b/mm/mm_heap/mm.h
index 4bb919ac1e7..10ee0596ac0 100644
--- a/mm/mm_heap/mm.h
+++ b/mm/mm_heap/mm.h
@@ -148,7 +148,7 @@
 #ifdef CONFIG_MM_SMALL
 typedef uint16_t mmsize_t;
 #else
-typedef uint32_t mmsize_t;
+typedef size_t mmsize_t;
 #endif
 
 /* This describes an allocated chunk.  An allocated chunk is