diff --git a/src/common/cache.c b/src/common/cache.c
index f478cf126311..83a2652c1a79 100644
--- a/src/common/cache.c
+++ b/src/common/cache.c
@@ -48,7 +48,7 @@ typedef struct dt_cache_bucket_t
   int16_t  write;  // number of writers (0 or 1)
   int32_t  lru;    // for garbage collection: lru list
   int32_t  mru;
-  int32_t  cost;   // cost associated with this entry (such as byte size)
+  size_t   cost;   // cost associated with this entry (such as byte size)
   uint32_t hash;   // hash of the element
   uint32_t key;    // key of the element
   // due to alignment, we waste 32 bits here
@@ -120,7 +120,7 @@ get_start_cacheline_bucket(const dt_cache_t *const cache, dt_cache_bucket_t *con
 
 static void
 add_cost(dt_cache_t    *cache,
-         const int32_t  cost)
+         const size_t   cost)
 {
   __sync_fetch_and_add(&cache->cost, cost);
 }
@@ -223,7 +223,7 @@ add_key_to_beginning_of_list(
   const uint32_t     hash,
   const uint32_t     key)
 {
-  int32_t cost = 1;
+  size_t cost = 1;
   if(cache->allocate)
   {
     // upgrade to a write lock in case the user requests it:
@@ -263,7 +263,7 @@ add_key_to_end_of_list(
   const uint32_t     key,
   dt_cache_bucket_t *const last_bucket)
 {
-  int32_t cost = 1;
+  size_t cost = 1;
   if(cache->allocate)
   {
     if(cache->allocate(cache->allocate_data, key, &cost, &free_bucket->data))
@@ -1096,7 +1096,7 @@ dt_cache_write_get(dt_cache_t *cache, const uint32_t key)
 }
 
 void
-dt_cache_realloc(dt_cache_t *cache, const uint32_t key, const int32_t cost, void *data)
+dt_cache_realloc(dt_cache_t *cache, const uint32_t key, const size_t cost, void *data)
 {
   // just to support different keys:
   const uint32_t hash = key;
@@ -1118,7 +1118,7 @@ dt_cache_realloc(dt_cache_t *cache, const uint32_t key, const int32_t cost, void
       assert(compare_bucket->write == 1);
       assert(compare_bucket->read == 1);
       compare_bucket->data = data;
-      const int32_t cost_diff = cost - compare_bucket->cost;
+      const size_t cost_diff = cost - compare_bucket->cost;
       compare_bucket->cost = cost;
       add_cost(cache, cost_diff);
       dt_cache_unlock(&segment->lock);
diff --git a/src/common/cache.h b/src/common/cache.h
index 05a4c98f91e0..d1de98e948d7 100644
--- a/src/common/cache.h
+++ b/src/common/cache.h
@@ -45,7 +45,7 @@ typedef struct dt_cache_t
   // allocate should return != 0 if a write lock on alloc is needed.
   // this might be useful for cases where the allocation takes a lot of time and you don't want
   // the hashtable spinlocks to block and wait for it.
-  int32_t (*allocate)(void *userdata, const uint32_t key, int32_t *cost, void **payload);
+  int32_t (*allocate)(void *userdata, const uint32_t key, size_t *cost, void **payload);
   void    (*cleanup) (void *userdata, const uint32_t key, void *payload);
   void *allocate_data;
   void *cleanup_data;
@@ -64,7 +64,7 @@ void dt_cache_static_allocation(dt_cache_t *cache, uint8_t *buf, const uint32_t
 static inline void
 dt_cache_set_allocate_callback(
   dt_cache_t *cache,
-  int32_t (*allocate)(void*, const uint32_t, int32_t*, void**),
+  int32_t (*allocate)(void*, const uint32_t, size_t*, void**),
   void *allocate_data)
 {
   cache->allocate = allocate;
@@ -115,7 +115,7 @@ void dt_cache_print(dt_cache_t *cache);
 void dt_cache_print_locked(dt_cache_t *cache);
 
 // replace data pointer, cleanup has to be done by the user.
-void dt_cache_realloc(dt_cache_t *cache, const uint32_t key, const int32_t cost, void *data);
+void dt_cache_realloc(dt_cache_t *cache, const uint32_t key, const size_t cost, void *data);
 
 // iterate over all currently contained data blocks.
 // not thread safe! only use this for init/cleanup!
diff --git a/src/common/image_cache.c b/src/common/image_cache.c
index 4af97746e7ce..7dc70199fbdc 100644
--- a/src/common/image_cache.c
+++ b/src/common/image_cache.c
@@ -27,7 +27,7 @@
 #include <sqlite3.h>
 
 int32_t
-dt_image_cache_allocate(void *data, const uint32_t key, int32_t *cost, void **buf)
+dt_image_cache_allocate(void *data, const uint32_t key, size_t *cost, void **buf)
 {
   dt_image_cache_t *c = (dt_image_cache_t *)data;
   const uint32_t hash = key; // == image id
diff --git a/src/common/mipmap_cache.c b/src/common/mipmap_cache.c
index 37c40b9bf6a6..fcf8ed992919 100644
--- a/src/common/mipmap_cache.c
+++ b/src/common/mipmap_cache.c
@@ -485,7 +485,7 @@ static void _init_f(float   *buf, uint32_t *width, uint32_t *height, const uint3
 static void _init_8(uint8_t *buf, uint32_t *width, uint32_t *height, const uint32_t imgid, const dt_mipmap_size_t size);
 
 static int32_t
-scratchmem_allocate(void *data, const uint32_t key, int32_t *cost, void **buf)
+scratchmem_allocate(void *data, const uint32_t key, size_t *cost, void **buf)
 {
   dt_mipmap_cache_one_t *c = (dt_mipmap_cache_one_t *)data;
   // slot is exactly aligned with encapsulated cache's position and already allocated
@@ -494,7 +494,7 @@ scratchmem_allocate(void *data, const uint32_t key, int32_t *cost, void **buf)
 }
 
 int32_t
-dt_mipmap_cache_allocate(void *data, const uint32_t key, int32_t *cost, void **buf)
+dt_mipmap_cache_allocate(void *data, const uint32_t key, size_t *cost, void **buf)
 {
   dt_mipmap_cache_one_t *c = (dt_mipmap_cache_one_t *)data;
   // slot is exactly aligned with encapsulated cache's position and already allocated
@@ -565,7 +565,7 @@ dt_mipmap_cache_alloc(dt_image_t *img, dt_mipmap_size_t size, dt_mipmap_cache_al
 
 // callback for the cache backend to initialize payload pointers
 int32_t
-dt_mipmap_cache_allocate_dynamic(void *data, const uint32_t key, int32_t *cost, void **buf)
+dt_mipmap_cache_allocate_dynamic(void *data, const uint32_t key, size_t *cost, void **buf)
 {
   dt_mipmap_cache_one_t *cache = (dt_mipmap_cache_one_t *)data;
   // for full image buffers