diff --git a/core/src/create.jl b/core/src/create.jl
index 5d0878d6f..a303a1c92 100644
--- a/core/src/create.jl
+++ b/core/src/create.jl
@@ -708,15 +708,6 @@ function User(db::DB, config::Config)::User
             errors = true
         end
 
-        for (col, id) in zip(interpolations, node_ids)
-            for (demand_p_itp, p_itp) in zip(col, priorities)
-                if any(demand_p_itp.u .< 0.0)
-                    @error "Demand of user node $id with priority #$p_itp should be non-negative"
-                    errors = true
-                end
-            end
-        end
-
         if !isnothing(first_row)
             min_level_ = coalesce(first_row.min_level, 0.0)
             return_factor_ = first_row.return_factor
diff --git a/core/src/solve.jl b/core/src/solve.jl
index ab37fd191..56dae81a2 100644
--- a/core/src/solve.jl
+++ b/core/src/solve.jl
@@ -415,6 +415,32 @@ struct User <: AbstractParameterNode
         allocated::Vector{Float64},
         abstracted::Vector{Float64},
     }
+
+    function User(
+        node_id,
+        active,
+        demand,
+        allocated,
+        return_factor,
+        min_level,
+        priorities,
+        record,
+    )
+        if valid_demand(node_id, demand, priorities)
+            return new(
+                node_id,
+                active,
+                demand,
+                allocated,
+                return_factor,
+                min_level,
+                priorities,
+                record,
+            )
+        else
+            error("Invalid demand")
+        end
+    end
 end
 
 "Subgrid linearly interpolates basin levels."
diff --git a/core/src/validation.jl b/core/src/validation.jl
index d49dc3506..4de1dad85 100644
--- a/core/src/validation.jl
+++ b/core/src/validation.jl
@@ -660,3 +660,21 @@ function valid_subgrid(
 
     return !errors
 end
+
+function valid_demand(
+    node_id::Vector{NodeID},
+    demand::Vector{Vector{ScalarInterpolation}},
+    priorities::Vector{Int},
+)::Bool
+    errors = false
+
+    for (col, id) in zip(demand, node_id)
+        for (demand_p_itp, p_itp) in zip(col, priorities)
+            if any(demand_p_itp.u .< 0.0)
+                @error "Demand of user node $id with priority #$p_itp should be non-negative"
+                errors = true
+            end
+        end
+    end
+    return !errors
+end