diff --git a/src/conversion.c b/src/conversion.c
index 17dce7f3..f5dd7ea2 100644
--- a/src/conversion.c
+++ b/src/conversion.c
@@ -434,10 +434,10 @@ _gpgme_strtoul_field (const char *string, unsigned long *result)
 /* Convert STRING into an offset value.  Note that this functions only
  * allows for a base-10 length.  This function is similar to atoi()
  * and thus there is no error checking.  */
-gpgme_off_t
+uint64_t
 _gpgme_string_to_off (const char *string)
 {
-  gpgme_off_t value = 0;
+  uint64_t value = 0;
 
   while (*string == ' ' || *string == '\t')
     string++;
diff --git a/src/data.c b/src/data.c
index e2de9f67..1bb334c9 100644
--- a/src/data.c
+++ b/src/data.c
@@ -572,7 +572,7 @@ gpgme_data_set_flag (gpgme_data_t dh, const char *name, const char *value)
     }
   else if (!strcmp (name, "io-buffer-size"))
     {
-      gpgme_off_t val;
+      uint64_t val;
 
       /* We may set this only once.  */
       if (dh->io_buffer_size)
@@ -744,7 +744,7 @@ _gpgme_data_get_fd (gpgme_data_t dh)
 
 
 /* Get the size-hint value for DH or 0 if not available.  */
-gpgme_off_t
+uint64_t
 _gpgme_data_get_size_hint (gpgme_data_t dh)
 {
   return dh ? dh->size_hint : 0;
diff --git a/src/data.h b/src/data.h
index 648d976f..3e063943 100644
--- a/src/data.h
+++ b/src/data.h
@@ -96,7 +96,7 @@ struct gpgme_data
   char *file_name;
 
   /* Hint on the to be expected total size of the data.  */
-  gpgme_off_t size_hint;
+  uint64_t size_hint;
 
   /* If no 0 the size of an allocated inbound or outpund buffers.  The
    * value is at least BUFFER_SIZE and capped at 1MiB.  */
@@ -189,7 +189,7 @@ void _gpgme_data_release (gpgme_data_t dh);
 int _gpgme_data_get_fd (gpgme_data_t dh);
 
 /* Get the size-hint value for DH or 0 if not available.  */
-gpgme_off_t _gpgme_data_get_size_hint (gpgme_data_t dh);
+uint64_t _gpgme_data_get_size_hint (gpgme_data_t dh);
 
 
 #endif	/* DATA_H */
diff --git a/src/engine-gpg.c b/src/engine-gpg.c
index 75e375d7..03e648f3 100644
--- a/src/engine-gpg.c
+++ b/src/engine-gpg.c
@@ -1774,7 +1774,7 @@ start (engine_gpg_t gpg)
 static gpgme_error_t
 add_input_size_hint (engine_gpg_t gpg, gpgme_data_t data)
 {
-  gpgme_off_t value = _gpgme_data_get_size_hint (data);
+  uint64_t value = _gpgme_data_get_size_hint (data);
   char numbuf[50];  /* Large enough for even 2^128 in base-10.  */
   char *p;
 
diff --git a/src/util.h b/src/util.h
index 90213b10..d3b982e7 100644
--- a/src/util.h
+++ b/src/util.h
@@ -35,6 +35,8 @@
 #ifdef HAVE_UNISTD_H
 # include <unistd.h>
 #endif
+#include <stdint.h>
+
 
 #include "gpgme.h"
 
@@ -143,7 +145,7 @@ int _gpgme_split_fields (char *string, char **array, int arraysize);
 gpgme_error_t _gpgme_strtoul_field (const char *string, unsigned long *result);
 
 /* Convert STRING into an offset value similar to atoi().  */
-gpgme_off_t _gpgme_string_to_off (const char *string);
+uint64_t _gpgme_string_to_off (const char *string);
 
 /* Parse the string TIMESTAMP into a time_t.  The string may either be
    seconds since Epoch or in the ISO 8601 format like