diff --git a/ape_array.c b/ape_array.c
index b3bf7e0..013fa7c 100644
--- a/ape_array.c
+++ b/ape_array.c
@@ -33,7 +33,7 @@ ape_array_t *ape_array_new(size_t n)
 }
 
 ape_array_item_t *ape_array_lookup_item(ape_array_t *array,
-        const char *key, int klen)
+        const char *key, size_t klen)
 {
     buffer *k, *v;
     if (!array) {
@@ -48,7 +48,7 @@ ape_array_item_t *ape_array_lookup_item(ape_array_t *array,
     return NULL;
 }
 
-buffer *ape_array_lookup(ape_array_t *array, const char *key, int klen)
+buffer *ape_array_lookup(ape_array_t *array, const char *key, size_t klen)
 {
     buffer *k, *v;
     if (!array) {
@@ -64,7 +64,7 @@ buffer *ape_array_lookup(ape_array_t *array, const char *key, int klen)
     return NULL;
 }
 
-buffer *ape_array_lookup_cstr(ape_array_t *array, const char *key, int klen)
+buffer *ape_array_lookup_cstr(ape_array_t *array, const char *key, size_t klen)
 {
     buffer *k, *v;
     if (!array) {
@@ -81,7 +81,7 @@ buffer *ape_array_lookup_cstr(ape_array_t *array, const char *key, int klen)
     return NULL;
 }
 
-void *ape_array_lookup_data(ape_array_t *array, const char *key, int klen)
+void *ape_array_lookup_data(ape_array_t *array, const char *key, size_t klen)
 {
     buffer *k, *v;
     if (!array) {
diff --git a/ape_array.h b/ape_array.h
index 6dc47eb..e398c25 100644
--- a/ape_array.h
+++ b/ape_array.h
@@ -52,10 +52,10 @@ extern "C" {
 
 ape_array_t *ape_array_new(size_t n);
 ape_array_item_t *ape_array_lookup_item(ape_array_t *array,
-        const char *key, int klen);
-buffer *ape_array_lookup(ape_array_t *array, const char *key, int klen);
-buffer *ape_array_lookup_cstr(ape_array_t *array, const char *key, int klen);
-void *ape_array_lookup_data(ape_array_t *array, const char *key, int klen);
+        const char *key, size_t klen);
+buffer *ape_array_lookup(ape_array_t *array, const char *key, size_t klen);
+buffer *ape_array_lookup_cstr(ape_array_t *array, const char *key, size_t klen);
+void *ape_array_lookup_data(ape_array_t *array, const char *key, size_t klen);
 
 ape_array_item_t *ape_array_add_b(ape_array_t *array, buffer *key, buffer *value);
 ape_array_item_t *ape_array_add_n(ape_array_t *array, const char *key, int klen, const char *value, int vlen);