diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 2a79090cd..2483132f6 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -445,12 +445,12 @@ EvalState::EvalState(
                     StorePathSet closure;
                     store->computeFSClosure(store->toStorePath(r.second).first, closure);
                     for (auto & path : closure)
-                        allowedPaths->insert(store->printStorePath(path));
+                        allowPath(store->printStorePath(path));
                 } catch (InvalidPath &) {
-                    allowedPaths->insert(r.second);
+                    allowPath(r.second);
                 }
             } else
-                allowedPaths->insert(r.second);
+                allowPath(r.second);
         }
     }
 
@@ -482,6 +482,12 @@ void EvalState::requireExperimentalFeatureOnEvaluation(
     }
 }
 
+void EvalState::allowPath(const Path & path)
+{
+    if (allowedPaths)
+        allowedPaths->insert(path);
+}
+
 Path EvalState::checkSourcePath(const Path & path_)
 {
     if (!allowedPaths) return path_;
@@ -1891,6 +1897,7 @@ string EvalState::copyPathToStore(PathSet & context, const Path & path)
         dstPath = store->printStorePath(p);
         srcToStore.insert_or_assign(path, std::move(p));
         printMsg(lvlChatty, "copied source '%1%' -> '%2%'", path, dstPath);
+        allowPath(dstPath);
     }
 
     context.insert(dstPath);
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 9df6150c6..f8c9cf5a7 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -150,6 +150,11 @@ public:
 
     SearchPath getSearchPath() { return searchPath; }
 
+    /* Allow access to a path. */
+    void allowPath(const Path & path);
+
+    /* Check whether access to a path is allowed and throw an error if
+       not. Otherwise return the canonicalised path. */
     Path checkSourcePath(const Path & path);
 
     void checkURI(const std::string & uri);
diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc
index 6a2902dff..abb0fb0be 100644
--- a/src/libexpr/flake/flake.cc
+++ b/src/libexpr/flake/flake.cc
@@ -64,8 +64,7 @@ static std::tuple<fetchers::Tree, FlakeRef, FlakeRef> fetchOrSubstituteTree(
     debug("got tree '%s' from '%s'",
         state.store->printStorePath(tree.storePath), lockedRef);
 
-    if (state.allowedPaths)
-        state.allowedPaths->insert(tree.actualPath);
+    state.allowPath(tree.actualPath);
 
     assert(!originalRef.input.getNarHash() || tree.storePath == originalRef.input.computeStorePath(*state.store));
 
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 749afadd0..1b79785ff 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1892,8 +1892,7 @@ static void addPath(EvalState & state, const Pos & pos, const string & name, con
 
     mkString(v, dstPath, {dstPath});
 
-    if (state.allowedPaths)
-        state.allowedPaths->insert(v.string.s);
+    state.allowPath(v.string.s);
 }
 
 
diff --git a/src/libexpr/primops/fetchMercurial.cc b/src/libexpr/primops/fetchMercurial.cc
index 3f88ccb91..b51b155f7 100644
--- a/src/libexpr/primops/fetchMercurial.cc
+++ b/src/libexpr/primops/fetchMercurial.cc
@@ -84,8 +84,7 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
         mkInt(*state.allocAttr(v, state.symbols.create("revCount")), *revCount);
     v.attrs->sort();
 
-    if (state.allowedPaths)
-        state.allowedPaths->insert(tree.actualPath);
+    state.allowPath(tree.actualPath);
 }
 
 static RegisterPrimOp r_fetchMercurial("fetchMercurial", 1, prim_fetchMercurial);
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index 1a69fe4e4..44f726f9b 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -169,8 +169,7 @@ static void fetchTree(
 
     auto [tree, input2] = input.fetch(state.store);
 
-    if (state.allowedPaths)
-        state.allowedPaths->insert(tree.actualPath);
+    state.allowPath(tree.actualPath);
 
     emitTreeAttrs(state, tree, input2, v, params.emptyRevFallback, false);
 }
@@ -245,8 +244,7 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
                 *url, expectedHash->to_string(Base32, true), hash.to_string(Base32, true));
     }
 
-    if (state.allowedPaths)
-        state.allowedPaths->insert(realPath);
+    state.allowPath(realPath);
 
     auto path = state.store->printStorePath(storePath);
     mkString(v, path, PathSet({path}));
diff --git a/src/nix/profile.cc b/src/nix/profile.cc
index c63ed9c88..96a20f673 100644
--- a/src/nix/profile.cc
+++ b/src/nix/profile.cc
@@ -98,10 +98,8 @@ struct ProfileManifest
 
         else if (pathExists(profile + "/manifest.nix")) {
             // FIXME: needed because of pure mode; ugly.
-            if (state.allowedPaths) {
-                state.allowedPaths->insert(state.store->followLinksToStore(profile));
-                state.allowedPaths->insert(state.store->followLinksToStore(profile + "/manifest.nix"));
-            }
+            state.allowPath(state.store->followLinksToStore(profile));
+            state.allowPath(state.store->followLinksToStore(profile + "/manifest.nix"));
 
             auto drvInfos = queryInstalled(state, state.store->followLinksToStore(profile));