diff --git a/src/os.c b/src/os.c
index a799cdf1..45182f64 100644
--- a/src/os.c
+++ b/src/os.c
@@ -8,8 +8,6 @@ terms of the MIT license. A copy of the license can be found in the file
 #define _DEFAULT_SOURCE   // ensure mmap flags are defined
 #endif
 
-#define MI_USE_SBRK
-
 #if defined(__sun)
 // illumos provides new mman.h api when any of these are defined
 // otherwise the old api based on caddr_t which predates the void pointers one.