diff --git a/src/common.h b/src/common.h
index b4c2ab98..f6337f8d 100644
--- a/src/common.h
+++ b/src/common.h
@@ -79,6 +79,14 @@
 #define MUST_TAIL
 #endif
 
+/* Assume that all POSIX-compatible environments provide mmap system call. */
+#if defined(_WIN32)
+#define HAVE_MMAP 0
+#else
+/* Assume POSIX-compatible runtime */
+#define HAVE_MMAP 1
+#endif
+
 /* Pattern Matching for C macros.
  * https://github.com/pfultz2/Cloak/wiki/C-Preprocessor-tricks,-tips,-and-idioms
  */
diff --git a/src/elf.c b/src/elf.c
index e123235a..ceb9c252 100644
--- a/src/elf.c
+++ b/src/elf.c
@@ -10,16 +10,14 @@
 #include "io.h"
 #include "utils.h"
 
-#if defined(_WIN32)
-/* fallback to standard I/O text stream */
-#include <stdio.h>
-#else
-/* Assume POSIX-compatible runtime */
-#define USE_MMAP 1
+#if HAVE_MMAP
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <unistd.h>
+#else
+/* fallback to standard I/O text stream */
+#include <stdio.h>
 #endif
 
 enum {
@@ -85,7 +83,7 @@ void elf_delete(elf_t *e)
         return;
 
     map_delete(e->symbols);
-#if defined(USE_MMAP)
+#if HAVE_MMAP
     if (e->raw_data)
         munmap(e->raw_data, e->raw_size);
 #else
@@ -97,7 +95,7 @@ void elf_delete(elf_t *e)
 /* release a loaded ELF file */
 static void release(elf_t *e)
 {
-#if !defined(USE_MMAP)
+#if !HAVE_MMAP
     free(e->raw_data);
 #endif
 
@@ -301,7 +299,7 @@ bool elf_open(elf_t *e, const char *input)
     if (!path)
         return false;
 
-#if defined(USE_MMAP)
+#if HAVE_MMAP
     int fd = open(path, O_RDONLY);
     if (fd < 0) {
         free(path);
@@ -353,7 +351,7 @@ bool elf_open(elf_t *e, const char *input)
         free(path);
         return false;
     }
-#endif /* USE_MMAP */
+#endif /* HAVE_MMAP */
 
     /* point to the header */
     e->hdr = (const struct Elf32_Ehdr *) e->raw_data;
diff --git a/src/io.c b/src/io.c
index a6273737..cbf5d3a4 100644
--- a/src/io.c
+++ b/src/io.c
@@ -8,8 +8,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#if !defined(_WIN32)
-#define USE_MMAP 1
+#if HAVE_MMAP
 #include <sys/mman.h>
 #include <unistd.h>
 #endif
@@ -32,7 +31,7 @@ static uint8_t *data_memory_base;
 memory_t *memory_new()
 {
     memory_t *mem = malloc(sizeof(memory_t));
-#if defined(USE_MMAP)
+#if HAVE_MMAP
     data_memory_base = mmap(NULL, MEM_SIZE, PROT_READ | PROT_WRITE,
                             MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
     if (data_memory_base == MAP_FAILED) {
@@ -53,7 +52,7 @@ memory_t *memory_new()
 
 void memory_delete(memory_t *mem)
 {
-#if defined(USE_MMAP)
+#if HAVE_MMAP
     munmap(mem->mem_base, MEM_SIZE);
 #else
     free(mem->mem_base);
diff --git a/src/mpool.c b/src/mpool.c
index feb8b194..0815b4bd 100644
--- a/src/mpool.c
+++ b/src/mpool.c
@@ -4,8 +4,7 @@
  */
 #include <stdlib.h>
 #include <string.h>
-#if !defined(_WIN32)
-#define USE_MMAP 1
+#if HAVE_MMAP
 #include <sys/mman.h>
 #include <unistd.h>
 #endif
@@ -31,7 +30,7 @@ typedef struct mpool {
 
 static void *mem_arena(size_t sz)
 {
-#if defined(USE_MMAP)
+#if HAVE_MMAP
     void *p =
         mmap(0, sz, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
     if (p == MAP_FAILED)
@@ -134,7 +133,7 @@ void mpool_free(mpool_t *mp, void *target)
 
 void mpool_destroy(mpool_t *mp)
 {
-#if defined(USE_MMAP)
+#if HAVE_MMAP
     size_t mem_size = mp->page_count * getpagesize();
     area_t *cur = &mp->area, *tmp = NULL;
     while (cur) {