diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index 8c6e2cdd9..3dc0c9935 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -27,6 +27,7 @@ import os, sys, subprocess, shutil, uuid, re
 from functools import wraps
 
 import importlib
+import copy
 
 run_depr_printed = False
 
@@ -91,6 +92,10 @@ class InterpreterObject():
             return self.methods[method_name](args, kwargs)
         raise InvalidCode('Unknown method "%s" in object.' % method_name)
 
+class MutableInterpreterObject(InterpreterObject):
+    def __init__(self):
+        super().__init__()
+
 class TryRunResultHolder(InterpreterObject):
     def __init__(self, res):
         super().__init__()
@@ -181,7 +186,7 @@ class ConfigureFileHolder(InterpreterObject):
         self.held_object = build.ConfigureFile(subdir, sourcename, targetname, configuration_data)
 
 
-class EnvironmentVariablesHolder(InterpreterObject):
+class EnvironmentVariablesHolder(MutableInterpreterObject):
     def __init__(self):
         super().__init__()
         self.held_object = build.EnvironmentVariables()
@@ -211,7 +216,7 @@ class EnvironmentVariablesHolder(InterpreterObject):
         self.add_var(self.held_object.prepend, args, kwargs)
 
 
-class ConfigurationDataHolder(InterpreterObject):
+class ConfigurationDataHolder(MutableInterpreterObject):
     def __init__(self):
         super().__init__()
         self.used = False # These objects become immutable after use in configure_file.
@@ -2455,6 +2460,9 @@ requirements use the version keyword argument instead.''')
         value = self.to_native(value)
         if not self.is_assignable(value):
             raise InvalidCode('Tried to assign an invalid value to variable.')
+        # For mutable objects we need to make a copy on assignment
+        if isinstance(value, MutableInterpreterObject):
+            value = copy.deepcopy(value)
         self.set_variable(var_name, value)
         return value
 
diff --git a/test cases/common/121 interpreter copy mutable var on assignment/meson.build b/test cases/common/121 interpreter copy mutable var on assignment/meson.build
new file mode 100644
index 000000000..8b15357ad
--- /dev/null
+++ b/test cases/common/121 interpreter copy mutable var on assignment/meson.build	
@@ -0,0 +1,20 @@
+project('foo', 'c')
+
+a = configuration_data()
+a.set('HELLO', 1)
+
+b = a
+
+assert(a.has('HELLO'), 'Original config data should be set on a')
+assert(b.has('HELLO'), 'Original config data should be set on copy')
+
+configure_file(output : 'b.h', configuration : b)
+
+# This should still work, as we didn't use the original above but a copy!
+a.set('WORLD', 1)
+
+assert(a.has('WORLD'), 'New config data should have been set')
+assert(not b.has('WORLD'), 'New config data set should not affect var copied earlier')
+
+configure_file(output : 'a.h', configuration : a)
+
diff --git a/test cases/common/48 test args/env2vars.c b/test cases/common/48 test args/env2vars.c
new file mode 100644
index 000000000..19250a8d5
--- /dev/null
+++ b/test cases/common/48 test args/env2vars.c	
@@ -0,0 +1,23 @@
+#include<stdio.h>
+#include<string.h>
+#include<stdlib.h>
+
+int main(int argc, char **argv) {
+    if(strcmp(getenv("first"), "something-else") != 0) {
+        fprintf(stderr, "First envvar is wrong. %s\n", getenv("first"));
+        return 1;
+    }
+    if(strcmp(getenv("second"), "val2") != 0) {
+        fprintf(stderr, "Second envvar is wrong.\n");
+        return 1;
+    }
+    if(strcmp(getenv("third"), "val3:and_more") != 0) {
+        fprintf(stderr, "Third envvar is wrong.\n");
+        return 1;
+    }
+    if(strstr(getenv("PATH"), "fakepath:") != NULL) {
+        fprintf(stderr, "Third envvar is wrong.\n");
+        return 1;
+    }
+    return 0;
+}
diff --git a/test cases/common/48 test args/meson.build b/test cases/common/48 test args/meson.build
index 640019863..f599bf7e2 100644
--- a/test cases/common/48 test args/meson.build	
+++ b/test cases/common/48 test args/meson.build	
@@ -2,6 +2,7 @@ project('test features', 'c')
 
 e1 = executable('cmd_args', 'cmd_args.c')
 e2 = executable('envvars', 'envvars.c')
+e3 = executable('env2vars', 'env2vars.c')
 
 env = environment()
 env.set('first', 'val1')
@@ -9,6 +10,12 @@ env.set('second', 'val2')
 env.set('third', 'val3', 'and_more', separator: ':')
 env.append('PATH', 'fakepath', separator: ':')
 
+# Make sure environment objects are copied on assignment and we can
+# change the copy without affecting the original environment object.
+env2 = env
+env2.set('first', 'something-else')
+
 test('command line arguments', e1, args : ['first', 'second'])
 test('environment variables', e2, env : env)
+test('environment variables 2', e3, env : env2)
 test('file arg', find_program('tester.py'), args : files('testfile.txt'))