diff --git a/delta.h b/delta.h
index 2df5fe13d9..8a56ec0799 100644
--- a/delta.h
+++ b/delta.h
@@ -90,15 +90,15 @@ static inline unsigned long get_delta_hdr_size(const unsigned char **datap,
 					       const unsigned char *top)
 {
 	const unsigned char *data = *datap;
-	unsigned long cmd, size = 0;
+	size_t cmd, size = 0;
 	int i = 0;
 	do {
 		cmd = *data++;
-		size |= (cmd & 0x7f) << i;
+		size |= st_left_shift(cmd & 0x7f, i);
 		i += 7;
 	} while (cmd & 0x80 && data < top);
 	*datap = data;
-	return size;
+	return cast_size_t_to_ulong(size);
 }
 
 #endif
diff --git a/object-file.c b/object-file.c
index c3d866a287..eb972cdccd 100644
--- a/object-file.c
+++ b/object-file.c
@@ -1306,7 +1306,7 @@ static void *unpack_loose_rest(git_zstream *stream,
 int parse_loose_header(const char *hdr, struct object_info *oi)
 {
 	const char *type_buf = hdr;
-	unsigned long size;
+	size_t size;
 	int type, type_len = 0;
 
 	/*
@@ -1341,12 +1341,12 @@ int parse_loose_header(const char *hdr, struct object_info *oi)
 			if (c > 9)
 				break;
 			hdr++;
-			size = size * 10 + c;
+			size = st_add(st_mult(size, 10), c);
 		}
 	}
 
 	if (oi->sizep)
-		*oi->sizep = size;
+		*oi->sizep = cast_size_t_to_ulong(size);
 
 	/*
 	 * The length must be followed by a zero byte
diff --git a/packfile.c b/packfile.c
index 89402cfc69..6423d77faa 100644
--- a/packfile.c
+++ b/packfile.c
@@ -1060,7 +1060,7 @@ unsigned long unpack_object_header_buffer(const unsigned char *buf,
 		unsigned long len, enum object_type *type, unsigned long *sizep)
 {
 	unsigned shift;
-	unsigned long size, c;
+	size_t size, c;
 	unsigned long used = 0;
 
 	c = buf[used++];
@@ -1074,10 +1074,10 @@ unsigned long unpack_object_header_buffer(const unsigned char *buf,
 			break;
 		}
 		c = buf[used++];
-		size += (c & 0x7f) << shift;
+		size = st_add(size, st_left_shift(c & 0x7f, shift));
 		shift += 7;
 	}
-	*sizep = size;
+	*sizep = cast_size_t_to_ulong(size);
 	return used;
 }