diff --git a/compiler/codegen/src/compile.rs b/compiler/codegen/src/compile.rs
index d5ae26d91..c64cfb897 100644
--- a/compiler/codegen/src/compile.rs
+++ b/compiler/codegen/src/compile.rs
@@ -1991,17 +1991,23 @@ impl Compiler {
         keys: &[Option<ast::Expr>],
         values: &[ast::Expr],
     ) -> CompileResult<()> {
-        emit!(self, Instruction::BuildMap { size: 0 });
-        for (key, value) in keys.iter().zip(values.iter()) {
-            if let Some(key) = key {
-                self.compile_expression(key)?;
-                self.compile_expression(value)?;
-                emit!(self, Instruction::MapAdd { i: 0 });
-            } else {
-                self.compile_expression(value)?;
-                emit!(self, Instruction::DictUpdate);
-            }
+        let mut size = 0;
+        let (packed, unpacked): (Vec<_>, Vec<_>) = keys
+            .iter()
+            .zip(values.iter())
+            .partition(|(k, _)| k.is_some());
+        for (key, value) in packed {
+            self.compile_expression(key.as_ref().unwrap())?;
+            self.compile_expression(value)?;
+            size += 1;
         }
+        emit!(self, Instruction::BuildMap { size });
+
+        for (_, value) in unpacked {
+            self.compile_expression(value)?;
+            emit!(self, Instruction::DictUpdate);
+        }
+
         Ok(())
     }