diff --git a/src/Mod/Assembly/App/AssemblyUtils.cpp b/src/Mod/Assembly/App/AssemblyUtils.cpp
index 8ab3c064fd..064b777ce0 100644
--- a/src/Mod/Assembly/App/AssemblyUtils.cpp
+++ b/src/Mod/Assembly/App/AssemblyUtils.cpp
@@ -199,11 +199,11 @@ DistanceType getDistanceType(App::DocumentObject* joint)
             return DistanceType::LinePlane;
         }
 
-        // Face + datum or unknown + datum → PlanePlane
-        // Datum on Reference1 for consistency with Face+Face path.
-        if (!datum1) {
-            swapJCS(joint);  // move datum from Ref2 → Ref1
-        }
+        // Face + datum or unknown + datum → PlanePlane.
+        // No swap needed: PlanarConstraint is symmetric (uses both
+        // z_i and z_j), and preserving the original Reference order
+        // keeps the initial Placement values consistent so the solver
+        // stays in the correct orientation branch.
         return DistanceType::PlanePlane;
     }