diff --git a/include/sigar_private.h b/include/sigar_private.h
index 84498086..7ff5618e 100644
--- a/include/sigar_private.h
+++ b/include/sigar_private.h
@@ -314,6 +314,9 @@ int sigar_group_name_get(sigar_t *sigar, int gid, char *buf, int buflen);
     fsusage->disk_read_bytes = fsusage->disk_write_bytes = \
     fsusage->disk_queue = fsusage->disk_time = SIGAR_FIELD_NOTIMPL;
 
+/* key used for filesystem (/) -> device (/dev/hda1) mapping */
+#define SIGAR_FSDEV_ID(sb) ((sb).st_ino + (sb).st_dev)
+
 #if defined(WIN32) || defined(NETWARE)
 int sigar_get_iftype(const char *name, int *type, int *inst);
 #endif
diff --git a/src/os/aix/aix_sigar.c b/src/os/aix/aix_sigar.c
index becca188..a72ed9df 100644
--- a/src/os/aix/aix_sigar.c
+++ b/src/os/aix/aix_sigar.c
@@ -1507,8 +1507,6 @@ int sigar_file_system_list_get(sigar_t *sigar,
 
 #define LSPV_CMD "/usr/sbin/lspv"
 
-#define FSDEV_ID(sb) (sb.st_ino + sb.st_dev)
-
 typedef struct {
     char *name;
     long addr;
@@ -1576,7 +1574,7 @@ static int create_diskmap_v4(sigar_t *sigar)
                 aix_diskio_t *diskio = malloc(sizeof(*diskio));
                 diskio->name = strdup(disk);
                 diskio->addr = -1;
-                ent = sigar_cache_get(sigar->diskmap, FSDEV_ID(sb));
+                ent = sigar_cache_get(sigar->diskmap, SIGAR_FSDEV_ID(sb));
                 ent->value = diskio;
             }
         }
@@ -1642,7 +1640,7 @@ static int create_diskmap_v5(sigar_t *sigar)
                     aix_diskio_t *diskio = malloc(sizeof(*diskio));
                     diskio->name = strdup(disk[i].name);
                     diskio->addr = -1;
-                    ent = sigar_cache_get(sigar->diskmap, FSDEV_ID(sb));
+                    ent = sigar_cache_get(sigar->diskmap, SIGAR_FSDEV_ID(sb));
                     ent->value = diskio;
                 }
 
@@ -1811,7 +1809,7 @@ int sigar_file_system_usage_get(sigar_t *sigar,
     status = stat(dirname, &sb);
     if (status == 0) {
         sigar_cache_entry_t *ent =
-            sigar_cache_get(sigar->diskmap, FSDEV_ID(sb));
+            sigar_cache_get(sigar->diskmap, SIGAR_FSDEV_ID(sb));
         if (!ent->value) {
             return SIGAR_OK;
         }
diff --git a/src/os/hpux/hpux_sigar.c b/src/os/hpux/hpux_sigar.c
index e14cb071..3412fb0c 100644
--- a/src/os/hpux/hpux_sigar.c
+++ b/src/os/hpux/hpux_sigar.c
@@ -560,8 +560,6 @@ int sigar_file_system_list_get(sigar_t *sigar,
 #define SIGAR_FS_BLOCKS_TO_BYTES(buf, f) \
     (((sigar_uint64_t)buf.f * (buf.f_bsize / 512)) >> 1)
 
-#define FSDEV_ID(sb) (sb.st_ino + sb.st_dev)
-
 static int create_fsdev_cache(sigar_t *sigar)
 {
     sigar_file_system_list_t fslist;
@@ -586,7 +584,7 @@ static int create_fsdev_cache(sigar_t *sigar)
                 continue;
             }
 
-            ent = sigar_cache_get(sigar->fsdev, FSDEV_ID(sb));
+            ent = sigar_cache_get(sigar->fsdev, SIGAR_FSDEV_ID(sb));
             ent->value = strdup(fsp->dev_name);
         }
     }
@@ -628,7 +626,7 @@ int sigar_file_system_usage_get(sigar_t *sigar,
         char *devname;
         int retval;
 
-        ent = sigar_cache_get(sigar->fsdev, FSDEV_ID(sb));
+        ent = sigar_cache_get(sigar->fsdev, SIGAR_FSDEV_ID(sb));
         if (ent->value == NULL) {
             return SIGAR_OK;
         }
diff --git a/src/os/linux/linux_sigar.c b/src/os/linux/linux_sigar.c
index 54f8a237..fb5c819b 100644
--- a/src/os/linux/linux_sigar.c
+++ b/src/os/linux/linux_sigar.c
@@ -1174,8 +1174,6 @@ int sigar_file_system_list_get(sigar_t *sigar,
     return SIGAR_OK;
 }
 
-#define FSDEV_ID(sb) (sb.st_ino + sb.st_dev)
-
 #define FSDEV_IS_DEV(dev) strnEQ(dev, "/dev/", 5)
 
 #define ST_MAJOR(sb) major((sb).st_rdev)
@@ -1204,7 +1202,7 @@ static iodev_t *get_fsdev(sigar_t *sigar,
         return NULL;
     }
 
-    id = FSDEV_ID(sb);
+    id = SIGAR_FSDEV_ID(sb);
 
     if (!sigar->fsdev) {
         sigar->fsdev = sigar_cache_new(15);
@@ -1241,7 +1239,7 @@ static iodev_t *get_fsdev(sigar_t *sigar,
                 return NULL; /* cant cache w/o inode */
             }
 
-            ent = sigar_cache_get(sigar->fsdev, FSDEV_ID(sb));
+            ent = sigar_cache_get(sigar->fsdev, SIGAR_FSDEV_ID(sb));
             if (ent->value) {
                 continue; /* already cached */
             }
diff --git a/src/os/solaris/solaris_sigar.c b/src/os/solaris/solaris_sigar.c
index 5eb3dcd4..59474095 100644
--- a/src/os/solaris/solaris_sigar.c
+++ b/src/os/solaris/solaris_sigar.c
@@ -1457,8 +1457,6 @@ static fsdev_path_t *get_fsdev_paths(sigar_t *sigar,
     return mapping;
 }
 
-#define FSDEV_ID(sb) (sb.st_ino + sb.st_dev)
-
 static int create_fsdev_cache(sigar_t *sigar)
 {
     fsdev_path_t *paths, *mapping;
@@ -1530,7 +1528,7 @@ static int create_fsdev_cache(sigar_t *sigar)
                         SIGAR_SSTRCPY(fs_kstat->module, paths->name);
                         fs_kstat->instance = paths->instance;
                         fs_kstat->partition = partition;
-                        ent = sigar_cache_get(sigar->fsdev, FSDEV_ID(sb));
+                        ent = sigar_cache_get(sigar->fsdev, SIGAR_FSDEV_ID(sb));
                         ent->value = fs_kstat;
 
                         if (debug) {
@@ -1650,7 +1648,7 @@ int sigar_file_system_usage_get(sigar_t *sigar,
     if (stat(dirname, &sb) < 0) {
         return SIGAR_OK;
     }
-    ent = sigar_cache_get(sigar->fsdev, FSDEV_ID(sb));
+    ent = sigar_cache_get(sigar->fsdev, SIGAR_FSDEV_ID(sb));
     if (ent->value == NULL) {
         return SIGAR_OK;
     }