diff --git a/dtool/src/dtoolutil/executionEnvironment.I b/dtool/src/dtoolutil/executionEnvironment.I
index d31122dd30..cf1ce5f493 100644
--- a/dtool/src/dtoolutil/executionEnvironment.I
+++ b/dtool/src/dtoolutil/executionEnvironment.I
@@ -40,6 +40,17 @@ get_environment_variable(const string &var) {
   return get_ptr()->ns_get_environment_variable(var);
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: ExecutionEnvironment::set_environment_variable
+//       Access: Public, Static
+//  Description: Changes the definition of the indicated environment
+//               variable.
+////////////////////////////////////////////////////////////////////
+INLINE void ExecutionEnvironment::
+set_environment_variable(const string &var, const string &value) {
+  return get_ptr()->ns_set_environment_variable(var, value);
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: ExecutionEnvironment::get_num_args
 //       Access: Public, Static
diff --git a/dtool/src/dtoolutil/executionEnvironment.cxx b/dtool/src/dtoolutil/executionEnvironment.cxx
index 6d6533f077..199ea1fb3a 100644
--- a/dtool/src/dtoolutil/executionEnvironment.cxx
+++ b/dtool/src/dtoolutil/executionEnvironment.cxx
@@ -195,6 +195,19 @@ ns_get_environment_variable(const string &var) const {
 #endif
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: ExecutionEnvironment::ns_set_environment_variable
+//       Access: Private
+//  Description: Changes the definition of the indicated environment
+//               variable.  The nonstatic implementation.
+////////////////////////////////////////////////////////////////////
+void ExecutionEnvironment::
+ns_set_environment_variable(const string &var, const string &value) {
+  _variables[var] = value;
+  string put = var + "=" + value;
+  putenv(put.c_str());
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: ExecutionEnvironment::ns_get_num_args
 //       Access: Private
diff --git a/dtool/src/dtoolutil/executionEnvironment.h b/dtool/src/dtoolutil/executionEnvironment.h
index ac40ef0ab8..d8a9f079ff 100644
--- a/dtool/src/dtoolutil/executionEnvironment.h
+++ b/dtool/src/dtoolutil/executionEnvironment.h
@@ -41,6 +41,7 @@ private:
 public:
   INLINE static bool has_environment_variable(const string &var);
   INLINE static string get_environment_variable(const string &var);
+  INLINE static void set_environment_variable(const string &var, const string &value);
 
   static string expand_string(const string &str);
 
@@ -54,6 +55,7 @@ public:
 private:
   bool ns_has_environment_variable(const string &var) const;
   string ns_get_environment_variable(const string &var) const;
+  void ns_set_environment_variable(const string &var, const string &value);
 
   int ns_get_num_args() const;
   string ns_get_arg(int n) const;