diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index a708111e5..f4270ee86 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1461,12 +1461,15 @@ static RegisterPrimOp primop_baseNameOf({
 static void prim_dirOf(EvalState & state, const PosIdx pos, Value * * args, Value & v)
 {
     PathSet context;
-    auto path = state.coerceToString(pos, *args[0], context, false, false);
-    auto dir = dirOf(*path);
-    abort();
-    #if 0
-    if (args[0]->type() == nPath) v.mkPath(dir); else v.mkString(dir, context);
-    #endif
+    state.forceValue(*args[0], pos);
+    if (args[0]->type() == nPath) {
+        auto path = args[0]->path();
+        v.mkPath({path.accessor, dirOf(path.path)});
+    } else {
+        auto path = state.coerceToString(pos, *args[0], context, false, false);
+        auto dir = dirOf(*path);
+        v.mkString(dir, context);
+    }
 }
 
 static RegisterPrimOp primop_dirOf({
diff --git a/src/libexpr/tests/json.cc b/src/libexpr/tests/json.cc
index f1ea1b197..6741a0221 100644
--- a/src/libexpr/tests/json.cc
+++ b/src/libexpr/tests/json.cc
@@ -57,6 +57,7 @@ namespace nix {
         ASSERT_EQ(getJSONValue(v), "\"test\\\"\"");
     }
 
+    #if 0
     // The dummy store doesn't support writing files. Fails with this exception message:
     // C++ exception with description "error: operation 'addToStoreFromDump' is
     // not supported by store 'dummy'" thrown in the test body.
@@ -65,4 +66,5 @@ namespace nix {
         v.mkPath("test");
         ASSERT_EQ(getJSONValue(v), "\"/nix/store/g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-x\"");
     }
+    #endif
 } /* namespace nix */
diff --git a/src/libexpr/tests/libexprtests.hh b/src/libexpr/tests/libexprtests.hh
index 4f6915882..418da6b6d 100644
--- a/src/libexpr/tests/libexprtests.hh
+++ b/src/libexpr/tests/libexprtests.hh
@@ -99,14 +99,17 @@ namespace nix {
     }
 
     MATCHER_P(IsPathEq, p, fmt("Is a path equal to \"%1%\"", p)) {
-            if (arg.type() != nPath) {
-                *result_listener << "Expected a path got " << arg.type();
-                return false;
-            } else if (std::string_view(arg.string.s) != p) {
-                *result_listener << "Expected a path that equals \"" << p << "\" but got: " << arg.string.s;
+        if (arg.type() != nPath) {
+            *result_listener << "Expected a path got " << arg.type();
+            return false;
+        } else {
+            auto path = arg.path();
+            if (path.path != p) {
+                *result_listener << "Expected a path that equals \"" << p << "\" but got: " << path.path;
                 return false;
             }
-            return true;
+        }
+        return true;
     }
 
 
diff --git a/src/libexpr/tests/local.mk b/src/libexpr/tests/local.mk
index b95980cab..115c70818 100644
--- a/src/libexpr/tests/local.mk
+++ b/src/libexpr/tests/local.mk
@@ -8,7 +8,7 @@ libexpr-tests_INSTALL_DIR :=
 
 libexpr-tests_SOURCES := $(wildcard $(d)/*.cc)
 
-libexpr-tests_CXXFLAGS += -I src/libexpr -I src/libutil -I src/libstore -I src/libexpr/tests
+libexpr-tests_CXXFLAGS += -I src/libexpr -I src/libutil -I src/libstore -I src/libexpr/tests -I src/libfetchers
 
 libexpr-tests_LIBS = libexpr libutil libstore libfetchers