diff --git a/CMakeLists.txt b/CMakeLists.txt
index cdccb8e4b..11a6ec2a4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -207,6 +207,17 @@ list(APPEND Z3_COMPONENT_EXTRA_INCLUDE_DIRS
   "${PROJECT_SOURCE_DIR}/src"
 )
 
+################################################################################
+# malloc_usable_size()
+################################################################################
+option(Z3_USE_MALLOC_USABLE_SIZE "Use malloc_usable_size (or equivalents like malloc_size or _msize)" ON)
+if (Z3_USE_MALLOC_USABLE_SIZE)
+  message(STATUS "Using malloc_usable_size")
+  list(APPEND Z3_COMPONENT_CXX_DEFINES "-DHAS_MALLOC_USABLE_SIZE")
+else()
+  message(STATUS "Not using malloc_usable_size")
+endif()
+
 ################################################################################
 # GNU multiple precision library support
 ################################################################################
diff --git a/src/util/memory_manager.cpp b/src/util/memory_manager.cpp
index 8c6bfc7e7..ac2e402f8 100644
--- a/src/util/memory_manager.cpp
+++ b/src/util/memory_manager.cpp
@@ -13,19 +13,17 @@ Copyright (c) 2015 Microsoft Corporation
 #include "util/error_codes.h"
 #include "util/debug.h"
 #include "util/scoped_timer.h"
-#ifdef __GLIBC__
+#ifndef HAS_MALLOC_USABLE_SIZE
+// drop calls to malloc_usable_size
+#elif defined(__GLIBC__)
 # include <malloc.h>
-# define HAS_MALLOC_USABLE_SIZE
 #elif defined(__APPLE__)
 # include <malloc/malloc.h>
-# define HAS_MALLOC_USABLE_SIZE
 # define malloc_usable_size malloc_size
 #elif defined(__FreeBSD__)
 # include <malloc_np.h>
-# define HAS_MALLOC_USABLE_SIZE
 #elif defined(_WINDOWS)
 # include <malloc.h>
-# define HAS_MALLOC_USABLE_SIZE
 # define malloc_usable_size _msize
 #endif