diff --git a/Source/cmFileCommand.cxx b/Source/cmFileCommand.cxx
index 4c288f5f21..402ceb24f0 100644
--- a/Source/cmFileCommand.cxx
+++ b/Source/cmFileCommand.cxx
@@ -208,16 +208,20 @@ bool cmFileCommand::HandleWriteCommand(std::vector<std::string> const& args,
   cmSystemTools::MakeDirectory(dir);
 
   mode_t mode = 0;
+  bool writable = false;
 
   // Set permissions to writable
   if (cmSystemTools::GetPermissions(fileName.c_str(), mode)) {
-    cmSystemTools::SetPermissions(fileName.c_str(),
 #if defined(_MSC_VER) || defined(__MINGW32__)
-                                  mode | S_IWRITE
+    writable = mode & S_IWRITE;
+    mode_t newMode = mode | S_IWRITE;
 #else
-                                  mode | S_IWUSR | S_IWGRP
+    writable = mode & S_IWUSR;
+    mode_t newMode = mode | S_IWUSR | S_IWGRP;
 #endif
-    );
+    if (!writable) {
+      cmSystemTools::SetPermissions(fileName.c_str(), newMode);
+    }
   }
   // If GetPermissions fails, pretend like it is ok. File open will fail if
   // the file is not writable
@@ -242,7 +246,7 @@ bool cmFileCommand::HandleWriteCommand(std::vector<std::string> const& args,
     return false;
   }
   file.close();
-  if (mode) {
+  if (mode && !writable) {
     cmSystemTools::SetPermissions(fileName.c_str(), mode);
   }
   return true;
diff --git a/Source/cmWriteFileCommand.cxx b/Source/cmWriteFileCommand.cxx
index d3d2db09a5..c504ef4360 100644
--- a/Source/cmWriteFileCommand.cxx
+++ b/Source/cmWriteFileCommand.cxx
@@ -45,16 +45,20 @@ bool cmWriteFileCommand::InitialPass(std::vector<std::string> const& args,
   cmSystemTools::MakeDirectory(dir);
 
   mode_t mode = 0;
+  bool writable = false;
 
   // Set permissions to writable
   if (cmSystemTools::GetPermissions(fileName.c_str(), mode)) {
-    cmSystemTools::SetPermissions(fileName.c_str(),
 #if defined(_MSC_VER) || defined(__MINGW32__)
-                                  mode | S_IWRITE
+    writable = mode & S_IWRITE;
+    mode_t newMode = mode | S_IWRITE;
 #else
-                                  mode | S_IWUSR | S_IWGRP
+    writable = mode & S_IWUSR;
+    mode_t newMode = mode | S_IWUSR | S_IWGRP;
 #endif
-    );
+    if (!writable) {
+      cmSystemTools::SetPermissions(fileName.c_str(), newMode);
+    }
   }
   // If GetPermissions fails, pretend like it is ok. File open will fail if
   // the file is not writable
@@ -69,7 +73,7 @@ bool cmWriteFileCommand::InitialPass(std::vector<std::string> const& args,
   }
   file << message << std::endl;
   file.close();
-  if (mode) {
+  if (mode && !writable) {
     cmSystemTools::SetPermissions(fileName.c_str(), mode);
   }