diff --git a/pkg/binfile/constraint_set.go b/pkg/binfile/constraint_set.go
index a17f04c..6692502 100644
--- a/pkg/binfile/constraint_set.go
+++ b/pkg/binfile/constraint_set.go
@@ -38,7 +38,7 @@ type column struct {
 	// information about the length of this column (e.g. its a
 	// multiple of two).  This seems only relevant for computed
 	// columns.
-	IntrinsicSizeFactor string `json:"intrinsic_size_factor"`
+	IntrinsicSizeFactor uint `json:"intrinsic_size_factor"`
 	// Indicates this is a computed column.  For binfiles being
 	// compiled without expansion, this should always be false.
 	Computed bool
@@ -82,6 +82,10 @@ type register struct {
 	// the original binfile format.  Instead, this field is determined from
 	// parsing the binfile format.
 	MustProve bool
+	// LengthMultiplier indicates the length multiplier for this column.  This
+	// must be a factor of the number of rows in the column.  For example, a
+	// column with length multiplier of 2 must have an even number of rows, etc.
+	LengthMultiplier uint `json:"length_multiplier"`
 }
 
 type columnSet struct {
@@ -168,8 +172,7 @@ func allocateRegisters(cs *constraintSet, schema *hir.Schema) map[uint]uint {
 		if !c.Computed {
 			handle := asHandle(c.Handle)
 			mid := registerModule(schema, handle.module)
-			// NOTE: assumption here that length multiplier is always one.
-			ctx := trace.NewContext(mid, 1)
+			ctx := trace.NewContext(mid, c.LengthMultiplier)
 			col_type := c.Type.toHir()
 			// Add column for this
 			cid := schema.AddDataColumn(ctx, handle.column, col_type)
diff --git a/pkg/schema/builder.go b/pkg/schema/builder.go
index 0e922c2..58436e1 100644
--- a/pkg/schema/builder.go
+++ b/pkg/schema/builder.go
@@ -96,8 +96,8 @@ func (tb TraceBuilder) Build(columns []trace.RawColumn) (trace.Trace, []error) {
 
 // A column key is used as a key for the column map
 type columnKey struct {
-	context trace.Context
-	column  string
+	module uint
+	column string
 }
 
 func (tb TraceBuilder) initialiseTrace(cols []trace.RawColumn) (*trace.ArrayTrace, []error) {
@@ -150,7 +150,7 @@ func (tb TraceBuilder) initialiseTraceColumns() ([]trace.ArrayColumn, map[column
 	for i, iter := uint(0), tb.schema.Columns(); iter.HasNext(); i++ {
 		c := iter.Next()
 		// Construct an appropriate key for this column
-		colkey := columnKey{c.Context(), c.Name()}
+		colkey := columnKey{c.Context().Module(), c.Name()}
 		// Initially column data and padding are nil.  In some cases, we will
 		// populate this information from the cols array.  However, in other
 		// cases, it will need to be populated during trace expansion.
@@ -180,12 +180,8 @@ func fillTraceColumns(modmap map[string]uint, colmap map[columnKey]uint,
 		if !ok {
 			errs = append(errs, fmt.Errorf("unknown module '%s' in trace", c.Module))
 		} else {
-			// We assume (for now) that user-provided columns always have a length
-			// multiplier of 1.  In general, this will be true.  However, in situations
-			// where we are importing expanded traces, then this might not be true.
-			context := trace.NewContext(mid, 1)
 			// Determine enclosiong module height
-			cid, ok := colmap[columnKey{context, c.Name}]
+			cid, ok := colmap[columnKey{mid, c.Name}]
 			// More sanity checks
 			if !ok {
 				errs = append(errs, fmt.Errorf("unknown column '%s' in trace", c.QualifiedName()))
diff --git a/pkg/trace/array_trace.go b/pkg/trace/array_trace.go
index 0313469..3716eb9 100644
--- a/pkg/trace/array_trace.go
+++ b/pkg/trace/array_trace.go
@@ -59,14 +59,14 @@ func (p *ArrayTrace) FillColumn(cid uint, data util.FrArray, padding fr.Element)
 	// Sanity check this column has not already been filled.
 	if data.Len()%multiplier != 0 {
 		colname := QualifiedColumnName(mod.name, col.name)
-		panic(fmt.Sprintf("computed column %s has invalid length multiplier (%d indivisible by %d)",
+		panic(fmt.Sprintf("column %s has invalid length multiplier (%d indivisible by %d)",
 			colname, data.Len(), multiplier))
 	} else if mod.height == math.MaxUint {
 		// Initialise column height
 		mod.height = data.Len() / col.context.multiplier
 	} else if data.Len() != p.Height(col.Context()) {
 		colname := QualifiedColumnName(mod.name, col.name)
-		panic(fmt.Sprintf("computed column %s has invalid height (%d but expected %d)", colname, data.Len(), mod.height))
+		panic(fmt.Sprintf("column %s has invalid height (%d but expected %d)", colname, data.Len(), mod.height*multiplier))
 	}
 	// Fill the column
 	col.fill(data, padding)
diff --git a/pkg/trace/context.go b/pkg/trace/context.go
index ad94a16..8fc9051 100644
--- a/pkg/trace/context.go
+++ b/pkg/trace/context.go
@@ -63,7 +63,7 @@ func (p Context) Module() uint {
 		panic("void context has no module")
 	}
 
-	panic("conflicted context has no module")
+	panic("conflicted context")
 }
 
 // LengthMultiplier returns the length multiplier for this context.  Note,