diff --git a/NEWS b/NEWS
index a68b001a..3a7d5180 100644
--- a/NEWS
+++ b/NEWS
@@ -7,6 +7,7 @@ Changes in 1.12 beta (XX Jan 2001):
   * implemented several new options for finer compression control:
       `--all-methods', `--all-filters' and `--brute'
   * linux/386: added the option `--force-execve'
+  * documentation updates
 
 Changes in 1.11 beta (20 Dec 2000):
   * UNSTABLE BETA VERSION - DO NOT USE EXCEPT FOR TESTING
diff --git a/src/main.cpp b/src/main.cpp
index 8f0eb121..c6f423a6 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -957,9 +957,13 @@ void upx_sanity_check(void)
     COMPILE_TIME_ASSERT(sizeof(long) >= 4);
     COMPILE_TIME_ASSERT(sizeof(void *) >= 4);
     COMPILE_TIME_ASSERT(sizeof(long) >= sizeof(void *));
-    COMPILE_TIME_ASSERT(((size_t) -1) > 0);
-    COMPILE_TIME_ASSERT(((ptrdiff_t) -1) < 0);
+
+    COMPILE_TIME_ASSERT(sizeof(off_t) >= sizeof(long));
     COMPILE_TIME_ASSERT(((off_t) -1) < 0);
+    COMPILE_TIME_ASSERT(sizeof(ptrdiff_t) >= sizeof(int));
+    COMPILE_TIME_ASSERT(((ptrdiff_t) -1) < 0);
+    COMPILE_TIME_ASSERT(sizeof(size_t) >= sizeof(int));
+    COMPILE_TIME_ASSERT(((size_t) -1) > 0);
 
     COMPILE_TIME_ASSERT(sizeof(BE16) == 2);
     COMPILE_TIME_ASSERT(sizeof(BE32) == 4);
diff --git a/src/p_unix.cpp b/src/p_unix.cpp
index 28103a86..207f03df 100644
--- a/src/p_unix.cpp
+++ b/src/p_unix.cpp
@@ -67,7 +67,7 @@ bool PackUnix::canPack()
 
     // info: currently the header is 36 (32+4) bytes before EOF
     unsigned char buf[256];
-    fi->seek(-(long)sizeof(buf), SEEK_END);
+    fi->seek(-(off_t)sizeof(buf), SEEK_END);
     fi->readx(buf, sizeof(buf));
     checkAlreadyPacked(buf, sizeof(buf));
 
diff --git a/src/packer.cpp b/src/packer.cpp
index 113fb111..edba4de9 100644
--- a/src/packer.cpp
+++ b/src/packer.cpp
@@ -497,7 +497,7 @@ void Packer::copyOverlay(OutputFile *fo, unsigned overlay,
     }
     info("Copying overlay: %d bytes", overlay);
     if (do_seek)
-        fi->seek(-(long)overlay, SEEK_END);
+        fi->seek(-(off_t)overlay, SEEK_END);
 
     // get buffer size, align to improve i/o speed
     unsigned buf_size = buf->getSize();