diff --git a/src/libexpr/common-eval-args.cc b/src/libexpr/common-eval-args.cc
index 37c74a94b..3e5400052 100644
--- a/src/libexpr/common-eval-args.cc
+++ b/src/libexpr/common-eval-args.cc
@@ -26,6 +26,13 @@ MixEvalArgs::MixEvalArgs()
         .description("add a path to the list of locations used to look up <...> file names")
         .label("path")
         .handler([&](std::string s) { searchPath.push_back(s); });
+
+    mkFlag()
+        .longName("impure")
+        .description("allow access to mutable paths and repositories")
+        .handler([&](std::vector<std::string> ss) {
+            evalSettings.pureEval = false;
+        });
 }
 
 Bindings * MixEvalArgs::getAutoArgs(EvalState & state)
diff --git a/src/nix/installables.cc b/src/nix/installables.cc
index fc2c34861..9bc5ff41f 100644
--- a/src/nix/installables.cc
+++ b/src/nix/installables.cc
@@ -20,13 +20,6 @@ SourceExprCommand::SourceExprCommand()
         .label("file")
         .description("evaluate a set of attributes from FILE (deprecated)")
         .dest(&file);
-
-    mkFlag()
-        .longName("impure")
-        .description("allow access to mutable paths and repositories")
-        .handler([&](std::vector<std::string> ss) {
-            evalSettings.pureEval = false;
-        });
 }
 
 ref<EvalState> SourceExprCommand::getEvalState()