diff --git a/hook/hook.go b/hook/hook.go
index 0f42478..d60ae26 100644
--- a/hook/hook.go
+++ b/hook/hook.go
@@ -13,6 +13,7 @@ import (
 	"log"
 	"net"
 	"net/textproto"
+	"os"
 	"reflect"
 	"regexp"
 	"strconv"
@@ -268,7 +269,6 @@ type Argument struct {
 	Source       string `json:"source,omitempty"`
 	Name         string `json:"name,omitempty"`
 	EnvName      string `json:"envname,omitempty"`
-	FileName     string `json:"filename,omitempty"`
 	Base64Decode bool   `json:"base64decode,omitempty"`
 	DeleteOnExit bool   `json:"deleteOnExit,omitempty"`
 }
@@ -497,7 +497,8 @@ func (h *Hook) ExtractCommandArgumentsForEnv(headers, query, payload *map[string
 
 // FileParameter describes a pass-file-to-command instance to be stored as file
 type FileParameter struct {
-	Filename     string
+	File         *os.File
+	EnvName      string
 	Data         []byte
 	DeleteOnExit bool
 }
@@ -511,10 +512,10 @@ func (h *Hook) ExtractCommandArgumentsForFile(headers, query, payload *map[strin
 	for i := range h.PassFileToCommand {
 		if arg, ok := h.PassFileToCommand[i].Get(headers, query, payload); ok {
 
-			if h.PassFileToCommand[i].FileName == "" {
-				// if no filename is set, fall-back on the name
-				log.Printf("no filename specified, falling back to  [%s]", EnvNamespace+h.PassFileToCommand[i].Name)
-				h.PassFileToCommand[i].FileName = EnvNamespace + h.PassFileToCommand[i].Name
+			if h.PassFileToCommand[i].EnvName == "" {
+				// if no environment-variable name is set, fall-back on the name
+				log.Printf("no ENVVAR name specified, falling back to [%s]", EnvNamespace+strings.ToUpper(h.PassFileToCommand[i].Name))
+				h.PassFileToCommand[i].EnvName = EnvNamespace + strings.ToUpper(h.PassFileToCommand[i].Name)
 			}
 
 			var fileContent []byte
@@ -528,7 +529,7 @@ func (h *Hook) ExtractCommandArgumentsForFile(headers, query, payload *map[strin
 				fileContent = []byte(arg)
 			}
 
-			args = append(args, FileParameter{Filename: h.PassFileToCommand[i].FileName, Data: fileContent, DeleteOnExit: h.PassFileToCommand[i].DeleteOnExit})
+			args = append(args, FileParameter{EnvName: h.PassFileToCommand[i].EnvName, Data: fileContent, DeleteOnExit: h.PassFileToCommand[i].DeleteOnExit})
 
 		} else {
 			errors = append(errors, &ArgumentError{h.PassFileToCommand[i]})
diff --git a/webhook.go b/webhook.go
index 492c2ac..fc943e5 100644
--- a/webhook.go
+++ b/webhook.go
@@ -331,8 +331,6 @@ func handleHook(h *hook.Hook, headers, query, payload *map[string]interface{}, b
 		}
 	}
 
-	cmd.Env = append(os.Environ(), envs...)
-
 	files, errors := h.ExtractCommandArgumentsForFile(headers, query, payload)
 
 	if errors != nil {
@@ -342,17 +340,24 @@ func handleHook(h *hook.Hook, headers, query, payload *map[string]interface{}, b
 	}
 
 	for i := range files {
-		if h.CommandWorkingDirectory != "" {
-			files[i].Filename = h.CommandWorkingDirectory + "/" + files[i].Filename
+		tmpfile, err := ioutil.TempFile(h.CommandWorkingDirectory, files[i].EnvName)
+		if err != nil {
+			log.Printf("error creating temp file [%s]", err)
+		}
+		log.Printf("writing env %s file %s", files[i].EnvName, tmpfile.Name())
+		if _, err := tmpfile.Write(files[i].Data); err != nil {
+			log.Printf("error writing file %s [%s]", tmpfile.Name(), err)
+		}
+		if err := tmpfile.Close(); err != nil {
+			log.Printf("error closing file %s [%s]", tmpfile.Name(), err)
 		}
 
-		log.Printf("writing file %s", files[i].Filename)
-		err := ioutil.WriteFile(files[i].Filename, files[i].Data, 0644)
-		if err != nil {
-			log.Printf("error writing file %s [%s]", files[i].Filename, err)
-		}
+		files[i].File = tmpfile
+		envs = append(envs, files[i].EnvName+"="+tmpfile.Name())
 	}
 
+	cmd.Env = append(os.Environ(), envs...)
+
 	log.Printf("executing %s (%s) with arguments %q and environment %s using %s as cwd\n", h.ExecuteCommand, cmd.Path, cmd.Args, envs, cmd.Dir)
 
 	out, err := cmd.CombinedOutput()
@@ -365,10 +370,10 @@ func handleHook(h *hook.Hook, headers, query, payload *map[string]interface{}, b
 
 	for i := range files {
 		if files[i].DeleteOnExit {
-			log.Printf("removing file: %s\n", files[i].Filename)
-			err := os.Remove(files[i].Filename)
+			log.Printf("removing file %s\n", files[i].File.Name())
+			err := os.Remove(files[i].File.Name())
 			if err != nil {
-				log.Printf("error removing file %s [%s]", files[i].Filename, err)
+				log.Printf("error removing file %s [%s]", files[i].File.Name(), err)
 			}
 		}
 	}