diff --git a/grep.c b/grep.c
index 733fd3a800..c23b95a808 100644
--- a/grep.c
+++ b/grep.c
@@ -864,9 +864,9 @@ void free_grep_patterns(struct grep_opt *opt)
 		free_pattern_expr(opt->pattern_expression);
 }
 
-static const char *end_of_line(const char *cp, unsigned long *left)
+static const char *end_of_line(const char *cp, size_t *left)
 {
-	unsigned long l = *left;
+	size_t l = *left;
 	while (l && *cp != '\n') {
 		l--;
 		cp++;
@@ -1454,7 +1454,7 @@ static int should_lookahead(struct grep_opt *opt)
 }
 
 static int look_ahead(struct grep_opt *opt,
-		      unsigned long *left_p,
+		      size_t *left_p,
 		      unsigned *lno_p,
 		      const char **bol_p)
 {
@@ -1567,7 +1567,7 @@ static int grep_source_1(struct grep_opt *opt, struct grep_source *gs, int colle
 {
 	const char *bol;
 	const char *peek_bol = NULL;
-	unsigned long left;
+	size_t left;
 	unsigned lno = 1;
 	unsigned last_hit = 0;
 	int binary_match_only = 0;
@@ -1737,7 +1737,7 @@ static int grep_source_1(struct grep_opt *opt, struct grep_source *gs, int colle
 			goto next_line;
 		}
 		if (show_function && (!peek_bol || peek_bol < bol)) {
-			unsigned long peek_left = left;
+			size_t peek_left = left;
 			const char *peek_eol = eol;
 
 			/*
@@ -1856,7 +1856,7 @@ int grep_source(struct grep_opt *opt, struct grep_source *gs)
 
 static void grep_source_init_buf(struct grep_source *gs,
 				 const char *buf,
-				 unsigned long size)
+				 size_t size)
 {
 	gs->type = GREP_SOURCE_BUF;
 	gs->name = NULL;
@@ -1867,7 +1867,7 @@ static void grep_source_init_buf(struct grep_source *gs,
 	gs->identifier = NULL;
 }
 
-int grep_buffer(struct grep_opt *opt, const char *buf, unsigned long size)
+int grep_buffer(struct grep_opt *opt, const char *buf, size_t size)
 {
 	struct grep_source gs;
 	int r;
@@ -1933,11 +1933,9 @@ void grep_source_clear_data(struct grep_source *gs)
 static int grep_source_load_oid(struct grep_source *gs)
 {
 	enum object_type type;
-	size_t size_st = 0;
 
 	gs->buf = odb_read_object(gs->repo->objects, gs->identifier,
-				  &type, &size_st);
-	gs->size = cast_size_t_to_ulong(size_st);
+				  &type, &gs->size);
 	if (!gs->buf)
 		return error(_("'%s': unable to read %s"),
 			     gs->name,
diff --git a/grep.h b/grep.h
index 13e26a9318..0bd705dfc0 100644
--- a/grep.h
+++ b/grep.h
@@ -212,7 +212,7 @@ void append_grep_pattern(struct grep_opt *opt, const char *pat, const char *orig
 void append_header_grep_pattern(struct grep_opt *, enum grep_header_field, const char *);
 void compile_grep_patterns(struct grep_opt *opt);
 void free_grep_patterns(struct grep_opt *opt);
-int grep_buffer(struct grep_opt *opt, const char *buf, unsigned long size);
+int grep_buffer(struct grep_opt *opt, const char *buf, size_t size);
 
 /* The field parameter is only used to filter header patterns
  * (where appropriate). If filtering isn't desirable
@@ -235,7 +235,7 @@ struct grep_source {
 	struct repository *repo; /* if GREP_SOURCE_OID */
 
 	const char *buf;
-	unsigned long size;
+	size_t size;
 
 	char *path; /* for attribute lookups */
 	struct userdiff_driver *driver;