diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc
index c94924371..5f021192b 100644
--- a/src/libexpr/flake/flake.cc
+++ b/src/libexpr/flake/flake.cc
@@ -57,7 +57,7 @@ static std::tuple<fetchers::Tree, FlakeRef, FlakeRef> fetchOrSubstituteTree(
         }
         flakeCache.push_back({originalRef, fetched.value()});
     }
-    
+
     auto [tree, lockedRef] = fetched.value();
 
     debug("got tree '%s' from '%s'",
diff --git a/src/libfetchers/fetchers.cc b/src/libfetchers/fetchers.cc
index 067db5e2e..d808aadd6 100644
--- a/src/libfetchers/fetchers.cc
+++ b/src/libfetchers/fetchers.cc
@@ -91,6 +91,7 @@ bool Input::operator ==(const Input & other) const
 
 bool Input::contains(const Input & other) const
 {
+    if (*this == other) return true;
     auto other2(other);
     other2.attrs.erase("ref");
     other2.attrs.erase("rev");
diff --git a/src/libfetchers/github.cc b/src/libfetchers/github.cc
index e704592f7..8dc9cb4bf 100644
--- a/src/libfetchers/github.cc
+++ b/src/libfetchers/github.cc
@@ -59,7 +59,7 @@ struct GitArchiveInputScheme : InputScheme
         }
 
         if (ref && rev)
-            throw BadURL("URL '%s' contains both a commit hash and a branch/tag name", url.url);
+            throw BadURL("URL '%s' contains both a commit hash and a branch/tag name %s %s", url.url, *ref, rev->gitRev());
 
         Input input;
         input.attrs.insert_or_assign("type", type());
@@ -115,14 +115,16 @@ struct GitArchiveInputScheme : InputScheme
         std::optional<Hash> rev) override
     {
         auto input(_input);
+        if (rev && ref)
+            throw BadURL("cannot apply both a commit hash (%s) and a branch/tag name ('%s') to input '%s'",
+                rev->gitRev(), *ref, input.to_string());
         if (rev) {
             input.attrs.insert_or_assign("rev", rev->gitRev());
             input.attrs.erase("ref");
         }
         if (ref) {
-            if (input.getRev())
-                throw BadURL("input '%s' contains both a commit hash and a branch/tag name", input.to_string());
             input.attrs.insert_or_assign("ref", *ref);
+            input.attrs.erase("rev");
         }
         return input;
     }