diff --git a/libmapper/internal.h b/libmapper/internal.h
index e6f9a07..836a5ec 100644
--- a/libmapper/internal.h
+++ b/libmapper/internal.h
@@ -1,8 +1,9 @@
 #pragma once
+#include <stddef.h>
 #ifdef __cplusplus
 extern "C" {
 #endif
-int sarraylen(char* array[]);
+size_t sarraylen(char* array[]);
 void sarrayfree(char* array[]);
 char** sarraydup(char* array[]);
 #ifdef __cplusplus
diff --git a/libmapper/mapper.c b/libmapper/mapper.c
index 1d00a32..8acc741 100644
--- a/libmapper/mapper.c
+++ b/libmapper/mapper.c
@@ -19,6 +19,7 @@
 
 #include <errno.h>
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -61,7 +62,7 @@
     sd_bus_slot* introspection_slot;
     sd_bus_slot* intf_slot;
     int* status;
-    int count;
+    size_t count;
     int finished;
     int r;
 };
@@ -102,9 +103,9 @@
 static int async_subtree_getpaths_callback(sd_bus_message*, void*,
                                            sd_bus_error*);
 
-int sarraylen(char* array[])
+size_t sarraylen(char* array[])
 {
-    int count = 0;
+    size_t count = 0;
     char** p = array;
 
     while (*p != NULL)
@@ -129,8 +130,8 @@
 
 char** sarraydup(char* array[])
 {
-    int count = sarraylen(array);
-    int i;
+    size_t count = sarraylen(array);
+    size_t i;
     char** ret = NULL;
 
     ret = calloc(count + 1, sizeof(*ret));
@@ -175,7 +176,8 @@
 static int async_wait_getobject_callback(sd_bus_message* m, void* userdata,
                                          _unused_ sd_bus_error* e)
 {
-    int i, r;
+    size_t i;
+    int r;
     struct async_wait_callback_data* data = userdata;
     mapper_async_wait* wait = data->wait;
     uint64_t next_retry;
@@ -235,7 +237,8 @@
 
 static int async_wait_get_objects(mapper_async_wait* wait)
 {
-    int i, r;
+    size_t i;
+    int r;
     struct async_wait_callback_data* data = NULL;
 
     for (i = 0; i < wait->count; ++i)
@@ -294,7 +297,7 @@
 
 static int async_wait_check_done(mapper_async_wait* w)
 {
-    int i;
+    size_t i;
 
     if (w->finished)
         return 1;