diff --git a/src/include/options.h b/src/include/options.h
index 64bee3c..b477a7e 100644
--- a/src/include/options.h
+++ b/src/include/options.h
@@ -14,6 +14,7 @@
 #endif
 
 #include <stdlib.h>
+#include <sys/types.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -42,13 +43,13 @@ struct opts_s {           /* structure describing run-time options */
 	bool linemode;                 /* count lines instead of bytes */
 	bool null_terminated_lines;    /* lines are null-terminated */
 	bool no_display;               /* do nothing other than pipe data */
-	size_t rate_limit;             /* rate limit, in bytes per second */
+	off_t rate_limit;              /* rate limit, in bytes per second */
 	size_t buffer_size;            /* buffer size, in bytes (0=default) */
 	unsigned int remote;           /* PID of pv to update settings of */
-	size_t size;                   /* total size of data */
+	off_t size;                    /* total size of data */
 	bool no_splice;                /* flag set if never to use splice */
 	unsigned int skip_errors;      /* skip read errors counter */
-	size_t error_skip_block;       /* skip block size, 0 for adaptive */
+	off_t error_skip_block;        /* skip block size, 0 for adaptive */
 	bool stop_at_size;             /* set if we stop at "size" bytes */
 	bool sync_after_write;         /* set if we sync after every write */
 	bool direct_io;                /* set if O_DIRECT is to be used */
diff --git a/src/include/pv-internal.h b/src/include/pv-internal.h
index 3bf141f..51ec1d7 100644
--- a/src/include/pv-internal.h
+++ b/src/include/pv-internal.h
@@ -36,8 +36,8 @@ extern "C" {
 #define REMOTE_INTERVAL		100000000	 /* nsec between checks for -R */
 #define BUFFER_SIZE		409600		 /* default transfer buffer size */
 #define BUFFER_SIZE_MAX		524288		 /* max auto transfer buffer size */
-#define MAX_READ_AT_ONCE	(size_t) 524288	 /* max to read() in one go */
-#define MAX_WRITE_AT_ONCE	(size_t) 524288	 /* max to write() in one go */
+#define MAX_READ_AT_ONCE	(off_t) 524288	 /* max to read() in one go */
+#define MAX_WRITE_AT_ONCE	(off_t) 524288	 /* max to write() in one go */
 #define TRANSFER_READ_TIMEOUT	0.09L		 /* seconds to time reads out at */
 #define TRANSFER_WRITE_TIMEOUT	0.9L		 /* seconds to time writes out at */
 
@@ -45,7 +45,7 @@ extern "C" {
 
 
 typedef struct pvhistory {
-	size_t total_bytes;
+	off_t total_bytes;
 	long double elapsed_sec;
 } pvhistory_t;
 
@@ -102,16 +102,16 @@ struct pvstate_s {
 	bool null_terminated_lines;      /* lines are null-terminated */
 	bool no_display;                 /* do nothing other than pipe data */
 	unsigned int skip_errors;        /* skip read errors counter */
-	size_t error_skip_block;         /* skip block size, 0 for adaptive */
+	off_t error_skip_block;          /* skip block size, 0 for adaptive */
 	bool stop_at_size;               /* set if we stop at "size" bytes */
 	bool sync_after_write;           /* set if we sync after every write */
 	bool direct_io;                  /* set if O_DIRECT is to be used */
 	bool direct_io_changed;          /* set when direct_io is changed */
 	bool no_splice;                  /* never use splice() */
 	bool discard_input;              /* write nothing to stdout */
-	size_t rate_limit;               /* rate limit, in bytes per second */
+	off_t rate_limit;                /* rate limit, in bytes per second */
 	size_t target_buffer_size;       /* buffer size (0=default) */
-	size_t size;                     /* total size of data */
+	off_t size;                      /* total size of data */
 	double interval;                 /* interval between updates */
 	double delay_start;              /* delay before first display */
 	unsigned int watch_pid;		 /* process to watch fds of */
@@ -167,7 +167,7 @@ struct pvstate_s {
 	int history_last;
 	long double current_avg_rate;    /* current average rate over last history intervals */
 	
-	size_t initial_offset;
+	off_t initial_offset;
 	/*@only@*/ char *display_buffer;
 	long display_buffer_size;
 	int lastoutput_length;		 /* number of last-output bytes to show */
@@ -245,7 +245,7 @@ struct pvstate_s {
 	 * This way, we're treating each input file separately.
 	 */
 	int last_read_skip_fd;
-	size_t read_errors_in_a_row;
+	off_t read_errors_in_a_row;
 	int read_error_warning_shown;
 #ifdef HAVE_SPLICE
 	/*
@@ -275,8 +275,8 @@ struct pvwatchfd_s {
 	char display_name[PV_SIZEOF_DISPLAY_NAME]; /* name to show on progress bar */
 	struct stat sb_fd;		 /* stat of fd symlink */
 	struct stat sb_fd_link;		 /* lstat of fd symlink */
-	size_t size;			 /* size of whole file, 0 if unknown */
-	ssize_t position;		 /* position last seen at */
+	off_t size;			 /* size of whole file, 0 if unknown */
+	off_t position;			 /* position last seen at */
 	struct timespec start_time;	 /* time we started watching the fd */
 };
 typedef struct pvwatchfd_s *pvwatchfd_t;
@@ -284,8 +284,8 @@ typedef struct pvwatchfd_s *pvwatchfd_t;
 void pv_error(pvstate_t, char *, ...);
 
 int pv_main_loop(pvstate_t);
-void pv_display(pvstate_t, long double, ssize_t, ssize_t);
-ssize_t pv_transfer(pvstate_t, int, bool *, bool *, size_t, long *);
+void pv_display(pvstate_t, long double, off_t, off_t);
+off_t pv_transfer(pvstate_t, int, bool *, bool *, off_t, long *);
 int pv_next_file(pvstate_t, unsigned int, int);
 /*@out@*/ const char *pv_current_file_name(pvstate_t);
 
diff --git a/src/include/pv.h b/src/include/pv.h
index 5450444..281320b 100644
--- a/src/include/pv.h
+++ b/src/include/pv.h
@@ -16,6 +16,7 @@
 #include <stdlib.h>
 #include <stdbool.h>
 #include <time.h>
+#include <sys/types.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -51,9 +52,9 @@ extern double pv_getnum_d(const char *);
 extern unsigned int pv_getnum_ui(const char *);
 
 /*
- * Return the given string converted to a size_t.
+ * Return the given string converted to an off_t.
  */
-extern size_t pv_getnum_size(const char *);
+extern off_t pv_getnum_size(const char *);
 
 /*
  * Return zero if the given string is a number of the given type. NB an
@@ -154,15 +155,15 @@ extern void pv_state_bits_set(pvstate_t, bool);
 extern void pv_state_null_terminated_lines_set(pvstate_t, bool);
 extern void pv_state_no_display_set(pvstate_t, bool);
 extern void pv_state_skip_errors_set(pvstate_t, unsigned int);
-extern void pv_state_error_skip_block_set(pvstate_t, size_t);
+extern void pv_state_error_skip_block_set(pvstate_t, off_t);
 extern void pv_state_stop_at_size_set(pvstate_t, bool);
 extern void pv_state_sync_after_write_set(pvstate_t, bool);
 extern void pv_state_direct_io_set(pvstate_t, bool);
-extern void pv_state_rate_limit_set(pvstate_t, size_t);
+extern void pv_state_rate_limit_set(pvstate_t, off_t);
 extern void pv_state_target_buffer_size_set(pvstate_t, size_t);
 extern void pv_state_no_splice_set(pvstate_t, bool);
 extern void pv_state_discard_input_set(pvstate_t, bool);
-extern void pv_state_size_set(pvstate_t, size_t);
+extern void pv_state_size_set(pvstate_t, off_t);
 extern void pv_state_interval_set(pvstate_t, double);
 extern void pv_state_width_set(pvstate_t, unsigned int, bool);
 extern void pv_state_height_set(pvstate_t, unsigned int, bool);
@@ -187,7 +188,7 @@ extern void pv_screensize(unsigned int *width, unsigned int *height);
 /*
  * Calculate the total size of all input files.
  */
-extern size_t pv_calc_total_size(pvstate_t);
+extern off_t pv_calc_total_size(pvstate_t);
 
 /*
  * Set up signal handlers ready for running the main loop.
diff --git a/src/main/options.c b/src/main/options.c
index 27d77bd..fd84628 100644
--- a/src/main/options.c
+++ b/src/main/options.c
@@ -376,7 +376,7 @@ opts_t opts_parse(unsigned int argc, char **argv)
 				memset(&sb, 0, sizeof(sb));
 				rc = stat(size_file, &sb);
 				if (0 == rc) {
-					opts->size = (size_t) (sb.st_size);
+					opts->size = (off_t) (sb.st_size);
 				} else {
 					/*@-mustfreefresh@ *//* see above */
 					fprintf(stderr, "%s: %s %s: %s\n",
@@ -420,7 +420,7 @@ opts_t opts_parse(unsigned int argc, char **argv)
 			opts->rate_limit = pv_getnum_size(optarg);
 			break;
 		case 'B':
-			opts->buffer_size = pv_getnum_size(optarg);
+			opts->buffer_size = (size_t) pv_getnum_size(optarg);
 			opts->no_splice = true;
 			break;
 		case 'C':
diff --git a/src/main/remote.c b/src/main/remote.c
index 8cde960..9b6e108 100644
--- a/src/main/remote.c
+++ b/src/main/remote.c
@@ -36,9 +36,9 @@ struct remote_msg {
 	bool bytes;			 /* bytes transferred flag */
 	bool bufpercent;		 /* transfer buffer percentage flag */
 	unsigned int lastwritten;	 /* last-written bytes count */
-	size_t rate_limit;		 /* rate limit, in bytes per second */
+	off_t rate_limit;		 /* rate limit, in bytes per second */
 	size_t buffer_size;		 /* buffer size, in bytes (0=default) */
-	size_t size;			 /* total size of data */
+	off_t size;			 /* total size of data */
 	double interval;		 /* interval between updates */
 	unsigned int width;		 /* screen width */
 	unsigned int height;		 /* screen height */
diff --git a/src/pv/display.c b/src/pv/display.c
index f9685a5..c9f85e3 100644
--- a/src/pv/display.c
+++ b/src/pv/display.c
@@ -1107,7 +1107,7 @@ static const char *pv__format(pvstate_t state,
  *
  * In line mode, "sl" and "tot" are in lines, not bytes.
  */
-void pv_display(pvstate_t state, long double esec, ssize_t sl, ssize_t tot)
+void pv_display(pvstate_t state, long double esec, off_t sl, off_t tot)
 {
 	const char *display;
 
diff --git a/src/pv/file.c b/src/pv/file.c
index bfdbdc6..b976532 100644
--- a/src/pv/file.c
+++ b/src/pv/file.c
@@ -33,9 +33,9 @@
  *
  * Returns the total size, or 0 if it is unknown.
  */
-static size_t pv_calc_total_bytes(pvstate_t state)
+static off_t pv_calc_total_bytes(pvstate_t state)
 {
-	size_t total;
+	off_t total;
 	struct stat sb;
 	unsigned int file_idx;
 
@@ -108,7 +108,7 @@ static size_t pv_calc_total_bytes(pvstate_t state)
 				off_t end_position;
 				end_position = lseek(fd, 0, SEEK_END);
 				if (end_position > 0) {
-					total += (size_t) end_position;
+					total += end_position;
 				}
 				(void) close(fd);
 			} else {
@@ -141,7 +141,7 @@ static size_t pv_calc_total_bytes(pvstate_t state)
 			end_position = lseek(STDOUT_FILENO, 0, SEEK_END);
 			total = 0;
 			if (end_position > 0) {
-				total = (size_t) end_position;
+				total = end_position;
 			}
 			if (lseek(STDOUT_FILENO, 0, SEEK_SET) != 0) {
 				pv_error(state, "%s: %s: %s", "(stdout)",
@@ -174,9 +174,9 @@ static size_t pv_calc_total_bytes(pvstate_t state)
  *
  * Returns the total size, or 0 if it is unknown.
  */
-static size_t pv_calc_total_lines(pvstate_t state)
+static off_t pv_calc_total_lines(pvstate_t state)
 {
-	size_t total;
+	off_t total;
 	struct stat sb;
 	unsigned int file_idx;
 
@@ -263,7 +263,7 @@ static size_t pv_calc_total_lines(pvstate_t state)
  *
  * Returns the total size, or 0 if it is unknown.
  */
-size_t pv_calc_total_size(pvstate_t state)
+off_t pv_calc_total_size(pvstate_t state)
 {
 	if (state->linemode) {
 		return pv_calc_total_lines(state);
diff --git a/src/pv/number.c b/src/pv/number.c
index e613545..c6cebfc 100644
--- a/src/pv/number.c
+++ b/src/pv/number.c
@@ -24,12 +24,12 @@ static bool pv__isdigit(char c)
 
 
 /*
- * Return the numeric value of "str", as a size_t.
+ * Return the numeric value of "str", as an off_t.
  */
-size_t pv_getnum_size(const char *str)
+off_t pv_getnum_size(const char *str)
 {
-	size_t n = 0;
-	size_t decimal = 0;
+	off_t n = 0;
+	off_t decimal = 0;
 	unsigned int decdivisor = 1;
 	unsigned int shift = 0;
 
@@ -41,7 +41,7 @@ size_t pv_getnum_size(const char *str)
 
 	for (; pv__isdigit(str[0]); str++) {
 		n = n * 10;
-		n += (size_t) (str[0] - '0');
+		n += (off_t) (str[0] - '0');
 	}
 
 	/*
@@ -52,7 +52,7 @@ size_t pv_getnum_size(const char *str)
 		for (; pv__isdigit(str[0]); str++) {
 			if (decdivisor < 10000) {
 				decimal = decimal * 10;
-				decimal += (size_t) (str[0] - '0');
+				decimal += (off_t) (str[0] - '0');
 				decdivisor = decdivisor * 10;
 			}
 		}
@@ -99,8 +99,8 @@ size_t pv_getnum_size(const char *str)
 		if (shiftby > 30)
 			shiftby = 30;
 
-		n = (size_t) (n << shiftby);
-		decimal = (size_t) (decimal << shiftby);
+		n = (off_t) (n << shiftby);
+		decimal = (off_t) (decimal << shiftby);
 		shift -= shiftby;
 	}
 
diff --git a/src/pv/state.c b/src/pv/state.c
index 40b8436..1b52b7c 100644
--- a/src/pv/state.c
+++ b/src/pv/state.c
@@ -246,7 +246,7 @@ void pv_state_skip_errors_set(pvstate_t state, unsigned int val)
 	state->skip_errors = val;
 }
 
-void pv_state_error_skip_block_set(pvstate_t state, size_t val)
+void pv_state_error_skip_block_set(pvstate_t state, off_t val)
 {
 	state->error_skip_block = val;
 }
@@ -272,7 +272,7 @@ void pv_state_discard_input_set(pvstate_t state, bool val)
 	state->discard_input = val;
 }
 
-void pv_state_rate_limit_set(pvstate_t state, size_t val)
+void pv_state_rate_limit_set(pvstate_t state, off_t val)
 {
 	state->rate_limit = val;
 }
@@ -287,7 +287,7 @@ void pv_state_no_splice_set(pvstate_t state, bool val)
 	state->no_splice = val;
 }
 
-void pv_state_size_set(pvstate_t state, size_t val)
+void pv_state_size_set(pvstate_t state, off_t val)
 {
 	state->size = val;
 }
diff --git a/src/pv/transfer.c b/src/pv/transfer.c
index 3c7dad3..0c650ef 100644
--- a/src/pv/transfer.c
+++ b/src/pv/transfer.c
@@ -784,7 +784,7 @@ static unsigned char *pv__allocate_aligned_buffer(int fd, size_t target_size)
  * state->exit_status is updated). In line mode, the number of lines written
  * will be put into *lineswritten.
  */
-ssize_t pv_transfer(pvstate_t state, int fd, bool *eof_in, bool *eof_out, size_t allowed, long *lineswritten)
+off_t pv_transfer(pvstate_t state, int fd, bool *eof_in, bool *eof_out, off_t allowed, long *lineswritten)
 {
 	bool ready_to_read, ready_to_write;
 	int check_read_fd, check_write_fd;