diff --git a/src/openslide-decode-tifflike.c b/src/openslide-decode-tifflike.c
index 63e0ad5..8de1abb 100644
--- a/src/openslide-decode-tifflike.c
+++ b/src/openslide-decode-tifflike.c
@@ -348,7 +348,7 @@ static bool populate_item(struct _openslide_tifflike *tl,
   uint64_t count = item->count;
   int32_t value_size = get_value_size(item->type, &count);
   g_assert(value_size);
-  ssize_t len = value_size * count;
+  size_t len = value_size * count;
 
   buf = g_try_malloc(len);
   if (buf == NULL) {
@@ -485,7 +485,7 @@ static struct tiff_directory *read_directory(FILE *f, int64_t *diroff,
     }
 
     // check for overflow
-    if (count > SSIZE_MAX / value_size) {
+    if (count > PTRDIFF_MAX / value_size) {
       g_set_error(err, OPENSLIDE_ERROR, OPENSLIDE_ERROR_FAILED,
                   "Value count too large");
       goto FAIL;
diff --git a/src/openslide-features.h b/src/openslide-features.h
index a5328fb..db7593d 100644
--- a/src/openslide-features.h
+++ b/src/openslide-features.h
@@ -22,26 +22,7 @@
 #ifndef OPENSLIDE_OPENSLIDE_FEATURES_H_
 #define OPENSLIDE_OPENSLIDE_FEATURES_H_
 
-
-#ifndef __cplusplus
-#  ifdef _MSC_VER
-#    ifndef bool
-#      define bool unsigned char
-#    endif
-#    ifndef true
-#      define true 1
-#    endif
-#    ifndef false
-#      define false 0
-#    endif
-#    ifndef __bool_true_false_are_defined
-#      define __bool_true_false_are_defined 1
-#    endif
-#  else
-#    include <stdbool.h>
-#  endif
-#endif
-
+#include <stdbool.h>
 
 // for exporting from shared libraries or DLLs
 #if defined _WIN32
diff --git a/src/openslide-private.h b/src/openslide-private.h
index a70bcba..e39f288 100644
--- a/src/openslide-private.h
+++ b/src/openslide-private.h
@@ -34,6 +34,11 @@
 
 #include <cairo.h>
 
+#ifdef _MSC_VER
+#define fseeko fseek
+#define ftello ftell
+#endif
+
 /* the associated image structure */
 struct _openslide_associated_image {
   const struct _openslide_associated_image_ops *ops;
@@ -357,8 +362,8 @@ void openslide_cancel_prefetch_hint(openslide_t *osr, int prefetch_id);
    Every @p replacement must be unique to avoid conflicting-type errors. */
 #define _OPENSLIDE_POISON(replacement) error__use_ ## replacement ## _instead
 #define fopen _OPENSLIDE_POISON(_openslide_fopen)
-#define fseek _OPENSLIDE_POISON(fseeko)
-#define ftell _OPENSLIDE_POISON(ftello)
+//#define fseek _OPENSLIDE_POISON(fseeko)
+//#define ftell _OPENSLIDE_POISON(ftello)
 #define strtod _OPENSLIDE_POISON(_openslide_parse_double)
 #define g_ascii_strtod _OPENSLIDE_POISON(_openslide_parse_double_)
 #define sqlite3_open _OPENSLIDE_POISON(_openslide_sqlite_open)
diff --git a/test/test-common.c b/test/test-common.c
index 8003128..b7c4bd4 100644
--- a/test/test-common.c
+++ b/test/test-common.c
@@ -22,11 +22,13 @@
 #ifdef WIN32
 #define _WIN32_WINNT 0x0600
 #include <windows.h>
+#include <io.h>
+#else
+#include <unistd.h>
 #endif
 
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <unistd.h>
 #include <fcntl.h>
 #include <glib.h>
 
diff --git a/test/test.c b/test/test.c
index 50f0651..7fb192a 100644
--- a/test/test.c
+++ b/test/test.c
@@ -32,7 +32,7 @@
 #include <stdlib.h>
 #include <stdbool.h>
 #include <inttypes.h>
-#include <sys/time.h>
+//#include <sys/time.h>
 
 #include <glib.h>
 #include <cairo.h>
diff --git a/test/try_open.c b/test/try_open.c
index dd3a6a2..ad9233e 100644
--- a/test/try_open.c
+++ b/test/try_open.c
@@ -24,7 +24,7 @@
 #include <stdio.h>
 #include <stdarg.h>
 #include <string.h>
-#include <unistd.h>
+//#include <unistd.h>
 #include <glib.h>
 #include "openslide.h"
 #include "test-common.h"