diff --git a/core/translate/emitter.rs b/core/translate/emitter.rs
index 4169ba617..79db8361b 100644
--- a/core/translate/emitter.rs
+++ b/core/translate/emitter.rs
@@ -824,7 +824,7 @@ fn emit_update_insns(
         program.emit_insn(Insn::Copy {
             src_reg: beg,
             dst_reg: beg + 1,
-            amount: 0,
+            extra_amount: 0,
         })
     }
 
@@ -941,14 +941,14 @@ fn emit_update_insns(
             program.emit_insn(Insn::Copy {
                 src_reg: idx_cols_start_reg + col.pos_in_table,
                 dst_reg: idx_start_reg + i,
-                amount: 0,
+                extra_amount: 0,
             });
         }
         // last register is the rowid
         program.emit_insn(Insn::Copy {
             src_reg: rowid_reg,
             dst_reg: idx_start_reg + num_cols,
-            amount: 0,
+            extra_amount: 0,
         });
 
         // this record will be inserted into the index later
@@ -1247,7 +1247,7 @@ pub fn emit_cdc_patch_record(
         program.emit_insn(Insn::Copy {
             src_reg: rowid_reg,
             dst_reg: columns_reg + rowid_alias_position,
-            amount: 0,
+            extra_amount: 0,
         });
         program.emit_insn(Insn::MakeRecord {
             start_reg: columns_reg,
@@ -1274,7 +1274,7 @@ pub fn emit_cdc_full_record(
             program.emit_insn(Insn::Copy {
                 src_reg: rowid_reg,
                 dst_reg: columns_reg + 1 + i,
-                amount: 0,
+                extra_amount: 0,
             });
         } else {
             program.emit_column(table_cursor_id, i, columns_reg + 1 + i);
@@ -1337,14 +1337,14 @@ pub fn emit_cdc_insns(
     program.emit_insn(Insn::Copy {
         src_reg: rowid_reg,
         dst_reg: turso_cdc_registers + 4,
-        amount: 0,
+        extra_amount: 0,
     });
 
     if let Some(before_record_reg) = before_record_reg {
         program.emit_insn(Insn::Copy {
             src_reg: before_record_reg,
             dst_reg: turso_cdc_registers + 5,
-            amount: 0,
+            extra_amount: 0,
         });
     } else {
         program.emit_null(turso_cdc_registers + 5, None);
@@ -1355,7 +1355,7 @@ pub fn emit_cdc_insns(
         program.emit_insn(Insn::Copy {
             src_reg: after_record_reg,
             dst_reg: turso_cdc_registers + 6,
-            amount: 0,
+            extra_amount: 0,
         });
     } else {
         program.emit_null(turso_cdc_registers + 6, None);
diff --git a/core/translate/expr.rs b/core/translate/expr.rs
index a3a639e15..706496edb 100644
--- a/core/translate/expr.rs
+++ b/core/translate/expr.rs
@@ -458,7 +458,7 @@ pub fn translate_expr(
         program.emit_insn(Insn::Copy {
             src_reg: reg,
             dst_reg: target_register,
-            amount: 0,
+            extra_amount: 0,
         });
         if let Some(span) = constant_span {
             program.constant_span_end(span);
@@ -1024,10 +1024,15 @@ pub fn translate_expr(
                         ScalarFunc::ConcatWs => {
                             let args = expect_arguments_min!(args, 2, srf);
 
-                            let temp_register = program.alloc_register();
-                            for arg in args.iter() {
-                                let reg = program.alloc_register();
-                                translate_expr(program, referenced_tables, arg, reg, resolver)?;
+                            let temp_register = program.alloc_registers(args.len() + 1);
+                            for (i, arg) in args.iter().enumerate() {
+                                translate_expr(
+                                    program,
+                                    referenced_tables,
+                                    arg,
+                                    temp_register + i + 1,
+                                    resolver,
+                                )?;
                             }
                             program.emit_insn(Insn::Function {
                                 constant_mask: 0,
@@ -1039,7 +1044,7 @@ pub fn translate_expr(
                             program.emit_insn(Insn::Copy {
                                 src_reg: temp_register,
                                 dst_reg: target_register,
-                                amount: 1,
+                                extra_amount: 0,
                             });
                             Ok(target_register)
                         }
@@ -1083,7 +1088,7 @@ pub fn translate_expr(
                             program.emit_insn(Insn::Copy {
                                 src_reg: temp_reg,
                                 dst_reg: target_register,
-                                amount: 0,
+                                extra_amount: 0,
                             });
 
                             Ok(target_register)
@@ -1569,7 +1574,7 @@ pub fn translate_expr(
                             program.emit_insn(Insn::Copy {
                                 src_reg: output_register,
                                 dst_reg: target_register,
-                                amount: 0,
+                                extra_amount: 0,
                             });
                             Ok(target_register)
                         }
@@ -1591,7 +1596,7 @@ pub fn translate_expr(
                             program.emit_insn(Insn::Copy {
                                 src_reg: output_register,
                                 dst_reg: target_register,
-                                amount: 0,
+                                extra_amount: 0,
                             });
                             Ok(target_register)
                         }
@@ -1746,7 +1751,7 @@ pub fn translate_expr(
                             program.emit_insn(Insn::Copy {
                                 src_reg: start_reg,
                                 dst_reg: target_register,
-                                amount: 0,
+                                extra_amount: 0,
                             });
                             Ok(target_register)
                         }
@@ -1980,7 +1985,7 @@ pub fn translate_expr(
                             .expect("Subquery result_columns_start_reg must be set")
                             + *column,
                         dst_reg: target_register,
-                        amount: 0,
+                        extra_amount: 0,
                     });
                     Ok(target_register)
                 }
diff --git a/core/translate/insert.rs b/core/translate/insert.rs
index 27de4a38b..868aacf50 100644
--- a/core/translate/insert.rs
+++ b/core/translate/insert.rs
@@ -379,7 +379,7 @@ pub fn translate_insert(
             program.emit_insn(Insn::Copy {
                 src_reg: reg,
                 dst_reg: rowid_reg,
-                amount: 0, // TODO: rename 'amount' to something else; amount==0 means 1
+                extra_amount: 0, // TODO: rename 'amount' to something else; amount==0 means 1
             });
             // for the row record, the rowid alias column is always set to NULL
             program.emit_insn(Insn::SoftNull { reg });
@@ -464,14 +464,14 @@ pub fn translate_insert(
             program.emit_insn(Insn::Copy {
                 src_reg: column_registers_start + col.0,
                 dst_reg: idx_start_reg + i,
-                amount: 0,
+                extra_amount: 0,
             });
         }
         // last register is the rowid
         program.emit_insn(Insn::Copy {
             src_reg: rowid_reg,
             dst_reg: idx_start_reg + num_cols,
-            amount: 0,
+            extra_amount: 0,
         });
 
         let index = schema
@@ -811,7 +811,7 @@ fn populate_columns_multiple_rows(
                 program.emit_insn(Insn::Copy {
                     src_reg: yield_reg + value_index_seen,
                     dst_reg: column_registers_start + value_index + other_values_seen,
-                    amount: 0,
+                    extra_amount: 0,
                 });
             }
 
diff --git a/core/translate/schema.rs b/core/translate/schema.rs
index fef50bb32..a1785f7f5 100644
--- a/core/translate/schema.rs
+++ b/core/translate/schema.rs
@@ -213,7 +213,7 @@ pub fn emit_schema_entry(
         program.emit_insn(Insn::Copy {
             src_reg: root_page_reg,
             dst_reg: rootpage_reg,
-            amount: 1,
+            extra_amount: 0,
         });
     }
 
diff --git a/core/translate/select.rs b/core/translate/select.rs
index abc3ba30e..a8ad0d737 100644
--- a/core/translate/select.rs
+++ b/core/translate/select.rs
@@ -741,7 +741,7 @@ pub fn emit_simple_count(
     program.emit_insn(Insn::Copy {
         src_reg: target_reg,
         dst_reg: output_reg,
-        amount: 0,
+        extra_amount: 0,
     });
     program.emit_result_row(output_reg, 1);
     Ok(())
diff --git a/core/translate/values.rs b/core/translate/values.rs
index a5e0f4142..28c037850 100644
--- a/core/translate/values.rs
+++ b/core/translate/values.rs
@@ -102,7 +102,7 @@ fn emit_toplevel_values(
         program.emit_insn(Insn::Copy {
             src_reg: start_reg + i,
             dst_reg: copy_start_reg + i,
-            amount: 0,
+            extra_amount: 0,
         });
     }
 
diff --git a/core/vdbe/execute.rs b/core/vdbe/execute.rs
index c1b1a2af5..5293310d0 100644
--- a/core/vdbe/execute.rs
+++ b/core/vdbe/execute.rs
@@ -5641,12 +5641,12 @@ pub fn op_copy(
     let Insn::Copy {
         src_reg,
         dst_reg,
-        amount,
+        extra_amount,
     } = insn
     else {
         unreachable!("unexpected Insn {:?}", insn)
     };
-    for i in 0..=*amount {
+    for i in 0..=*extra_amount {
         state.registers[*dst_reg + i] = state.registers[*src_reg + i].clone();
     }
     state.pc += 1;
diff --git a/core/vdbe/explain.rs b/core/vdbe/explain.rs
index 339bf303c..38981da29 100644
--- a/core/vdbe/explain.rs
+++ b/core/vdbe/explain.rs
@@ -1230,12 +1230,12 @@ pub fn insn_to_str(
             Insn::Copy {
                 src_reg,
                 dst_reg,
-                amount,
+                extra_amount,
             } => (
                 "Copy",
                 *src_reg as i32,
                 *dst_reg as i32,
-                *amount as i32,
+                *extra_amount as i32,
                 Value::build_text(""),
                 0,
                 format!("r[{dst_reg}]=r[{src_reg}]"),
diff --git a/core/vdbe/insn.rs b/core/vdbe/insn.rs
index f094f3db0..37acbc5e3 100644
--- a/core/vdbe/insn.rs
+++ b/core/vdbe/insn.rs
@@ -800,7 +800,7 @@ pub enum Insn {
     Copy {
         src_reg: usize,
         dst_reg: usize,
-        amount: usize, // 0 amount means we include src_reg, dst_reg..=dst_reg+amount = src_reg..=src_reg+amount
+        extra_amount: usize, // 0 extra_amount means we include src_reg, dst_reg..=dst_reg+amount = src_reg..=src_reg+amount
     },
 
     /// Allocate a new b-tree.
diff --git a/testing/scalar-functions.test b/testing/scalar-functions.test
index 807c4971d..8ab2ce2b6 100755
--- a/testing/scalar-functions.test
+++ b/testing/scalar-functions.test
@@ -35,6 +35,10 @@ do_execsql_test concat_ws-multiple {
   select concat_ws(',', 1, 2), concat_ws(',', 3, 4)
 } {1,2|3,4}
 
+do_execsql_test concat_ws-complex-args {
+  select concat_ws(',', 'a' || 'b', 'b' || 'c', 'c' || 'd');
+} {ab,bc,cd}
+
 do_execsql_test char {
   select char(108, 105)
 } {li}