diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 0bd03b232..5bd262071 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -2022,8 +2022,13 @@ static void prim_dirOf(EvalState & state, const PosIdx pos, Value ** args, Value
         NixStringContext context;
         auto path = state.coerceToString(
             pos, *args[0], context, "while evaluating the first argument passed to 'builtins.dirOf'", false, false);
-        auto dir = dirOf(*path);
-        v.mkString(dir, context);
+        auto pos = path->rfind('/');
+        if (pos == path->npos)
+            v.mkStringMove(".", context);
+        else if (pos == 0)
+            v.mkStringMove("/", context);
+        else
+            v.mkString(path->substr(0, pos), context);
     }
 }
 
diff --git a/tests/functional/lang/eval-okay-builtins-dirOf.exp b/tests/functional/lang/eval-okay-builtins-dirOf.exp
index 1130b1510..e0093e93a 100644
--- a/tests/functional/lang/eval-okay-builtins-dirOf.exp
+++ b/tests/functional/lang/eval-okay-builtins-dirOf.exp
@@ -1 +1 @@
-{ pathDoesntExistNested1 = /totallydoesntexistreally; pathDoesntExistNested2 = /totallydoesntexistreally/subdir1; pathDoesntExistRoot = /; pathRoot = /; stringEmpty = "."; stringMultipleSeps = "a"; stringNoSep = "."; stringRoot = "/"; stringRootA = "/"; stringRootSlash = "//"; stringRootSlashSlash = "///"; stringSingleDir = "a"; stringWithDot = "a/b/c/."; stringWithDotAndDotDot = "a/b/c/../."; stringWithDotAndDotDotSep2 = "a/b/c/../."; stringWithDotDot = "a/b/c/.."; stringWithDotDotSep2 = "a/b/c/.."; stringWithDotSep2 = "a/b/c/."; }
+{ pathDoesntExistNested1 = /totallydoesntexistreally; pathDoesntExistNested2 = /totallydoesntexistreally/subdir1; pathDoesntExistRoot = /; pathRoot = /; stringEmpty = "."; stringMultipleSeps = "a//"; stringNoSep = "."; stringRoot = "/"; stringRootA = "/"; stringRootSlash = "/"; stringRootSlashSlash = "//"; stringSingleDir = "a"; stringWithDot = "a/b/c/."; stringWithDotAndDotDot = "a/b/c/../."; stringWithDotAndDotDotSep2 = "a/b/c/.././"; stringWithDotDot = "a/b/c/.."; stringWithDotDotSep2 = "a/b/c/../"; stringWithDotSep2 = "a/b/c/./"; }