diff --git a/data_sizes.h b/data_sizes.h
index 3b747b3ea..cf52ae4f8 100644
--- a/data_sizes.h
+++ b/data_sizes.h
@@ -48,7 +48,7 @@ extern "C" {
 //             Sow[i*HashBytes]; j++]]]][[2]][[1]]
 
 
-static const size_t dag_sizes[2048] = {
+static const uint64_t dag_sizes[2048] = {
         1073739904U, 1082130304U, 1090514816U, 1098906752U, 1107293056U,
         1115684224U, 1124070016U, 1132461952U, 1140849536U, 1149232768U,
         1157627776U, 1166013824U, 1174404736U, 1182786944U, 1191180416U,
@@ -477,7 +477,7 @@ static const size_t dag_sizes[2048] = {
 //         While[! PrimeQ[i], i--];
 //         Sow[i*HashBytes]; j++]]]][[2]][[1]]
 
-const size_t cache_sizes[2048] = {
+const uint64_t cache_sizes[2048] = {
         16776896U, 16907456U, 17039296U, 17170112U, 17301056U, 17432512U, 17563072U,
         17693888U, 17824192U, 17955904U, 18087488U, 18218176U, 18349504U, 18481088U,
         18611392U, 18742336U, 18874304U, 19004224U, 19135936U, 19267264U, 19398208U,
diff --git a/ethash.h b/ethash.h
index a7159de65..b5ea8113c 100644
--- a/ethash.h
+++ b/ethash.h
@@ -43,8 +43,8 @@ extern "C" {
 #endif
 
 typedef struct ethash_params {
-    size_t full_size;               // Size of full data set (in bytes, multiple of mix size (128)).
-    size_t cache_size;              // Size of compute cache (in bytes, multiple of node size (64)).
+    uint64_t full_size;               // Size of full data set (in bytes, multiple of mix size (128)).
+    uint64_t cache_size;              // Size of compute cache (in bytes, multiple of node size (64)).
 } ethash_params;
 
 typedef struct ethash_return_value {
@@ -52,8 +52,8 @@ typedef struct ethash_return_value {
     uint8_t mix_hash[32];
 } ethash_return_value;
 
-size_t ethash_get_datasize(const uint32_t block_number);
-size_t ethash_get_cachesize(const uint32_t block_number);
+uint64_t ethash_get_datasize(const uint32_t block_number);
+uint64_t ethash_get_cachesize(const uint32_t block_number);
 
 // initialize the parameters
 static inline void ethash_params_init(ethash_params *params, const uint32_t block_number) {
diff --git a/internal.c b/internal.c
index 0a7e767e7..fed865094 100644
--- a/internal.c
+++ b/internal.c
@@ -37,12 +37,12 @@
 #include "sha3.h"
 #endif // WITH_CRYPTOPP
 
-size_t ethash_get_datasize(const uint32_t block_number) {
+uint64_t ethash_get_datasize(const uint32_t block_number) {
     assert(block_number / EPOCH_LENGTH < 2048);
     return dag_sizes[block_number / EPOCH_LENGTH];
 }
 
-size_t ethash_get_cachesize(const uint32_t block_number) {
+uint64_t ethash_get_cachesize(const uint32_t block_number) {
     assert(block_number / EPOCH_LENGTH < 2048);
     return cache_sizes[block_number / EPOCH_LENGTH];
 }