diff --git a/test/unittest/encodedstreamtest.cpp b/test/unittest/encodedstreamtest.cpp
index a29cb3b..3580608 100644
--- a/test/unittest/encodedstreamtest.cpp
+++ b/test/unittest/encodedstreamtest.cpp
@@ -158,9 +158,7 @@ protected:
         // Test FileWriteStream
         {
             char filename[L_tmpnam];
-            TempFilename(filename);
-
-            FILE *fp = fopen(filename, "wb");
+            FILE* fp = TempFile(filename);
             char buffer[16];
             FileWriteStream os(fp, buffer, sizeof(buffer));
             EncodedOutputStream<FileEncoding, FileWriteStream> eos(os, putBOM);
@@ -193,9 +191,8 @@ protected:
         // Test FileWriteStream
         {
             char filename[L_tmpnam];
-            TempFilename(filename);
+            FILE* fp = TempFile(filename);
 
-            FILE *fp = fopen(filename, "wb");
             char buffer[16];
             FileWriteStream os(fp, buffer, sizeof(buffer));
             AutoUTFOutputStream<unsigned, FileWriteStream> eos(os, type, putBOM);
diff --git a/test/unittest/filestreamtest.cpp b/test/unittest/filestreamtest.cpp
index c3217fa..b3f951a 100644
--- a/test/unittest/filestreamtest.cpp
+++ b/test/unittest/filestreamtest.cpp
@@ -98,9 +98,8 @@ TEST_F(FileStreamTest, FileReadStream) {
 
 TEST_F(FileStreamTest, FileWriteStream) {
     char filename[L_tmpnam];
-    TempFilename(filename);
+    FILE* fp = TempFile(filename);
 
-    FILE *fp = fopen(filename, "wb");
     char buffer[65536];
     FileWriteStream os(fp, buffer, sizeof(buffer));
     for (size_t i = 0; i < length_; i++)
diff --git a/test/unittest/unittest.h b/test/unittest/unittest.h
index 0330d73..a476db7 100644
--- a/test/unittest/unittest.h
+++ b/test/unittest/unittest.h
@@ -67,13 +67,21 @@ inline Ch* StrDup(const Ch* str) {
     return buffer;
 }
 
-inline void TempFilename(char *filename) {
+inline FILE* TempFile(char *filename) {
+#if _MSC_VER
     filename = tmpnam(filename);
 
     // For Visual Studio, tmpnam() adds a backslash in front. Remove it.
     if (filename[0] == '\\')
         for (int i = 0; filename[i] != '\0'; i++)
             filename[i] = filename[i + 1];
+        
+    return fopen(filename, "wb");
+#else
+    strcpy(filename, "/tmp/fileXXXXXX");
+    int fd = mkstemp(filename);
+    return fdopen(fd, "w");
+#endif
 }
 
 // Use exception for catching assert