diff --git a/src/libutil/args.cc b/src/libutil/args.cc
index ee0c99c2a..f6740e076 100644
--- a/src/libutil/args.cc
+++ b/src/libutil/args.cc
@@ -220,17 +220,27 @@ Args::Flag Args::Flag::mkHashTypeFlag(std::string && longName, HashType * ht)
     };
 }
 
-void completePath(size_t, std::string_view prefix)
+static void completePath(std::string_view prefix, int flags)
 {
     pathCompletions = true;
     glob_t globbuf;
-    if (glob((std::string(prefix) + "*").c_str(), GLOB_NOESCAPE | GLOB_TILDE, nullptr, &globbuf) == 0) {
+    if (glob((std::string(prefix) + "*").c_str(), GLOB_NOESCAPE | GLOB_TILDE | flags, nullptr, &globbuf) == 0) {
         for (size_t i = 0; i < globbuf.gl_pathc; ++i)
             completions->insert(globbuf.gl_pathv[i]);
         globfree(&globbuf);
     }
 }
 
+void completePath(size_t, std::string_view prefix)
+{
+    completePath(prefix, 0);
+}
+
+void completeDir(size_t, std::string_view prefix)
+{
+    completePath(prefix, GLOB_ONLYDIR);
+}
+
 Strings argvToStrings(int argc, char * * argv)
 {
     Strings args;
diff --git a/src/libutil/args.hh b/src/libutil/args.hh
index 250244162..405ec3d47 100644
--- a/src/libutil/args.hh
+++ b/src/libutil/args.hh
@@ -277,4 +277,6 @@ std::optional<std::string> needsCompletion(std::string_view s);
 
 void completePath(size_t, std::string_view prefix);
 
+void completeDir(size_t, std::string_view prefix);
+
 }
diff --git a/src/nix/installables.cc b/src/nix/installables.cc
index ade8f83f9..5ba48d69a 100644
--- a/src/nix/installables.cc
+++ b/src/nix/installables.cc
@@ -109,7 +109,7 @@ Strings SourceExprCommand::getDefaultFlakeAttrPathPrefixes()
 
 void SourceExprCommand::completeInstallable(std::string_view prefix)
 {
-    completePath(0, prefix);
+    completeDir(0, prefix);
 
     if (file) return; // FIXME