diff --git a/flatehr/build.py b/flatehr/build.py
index bbae540..b8a43ae 100644
--- a/flatehr/build.py
+++ b/flatehr/build.py
@@ -24,7 +24,7 @@ def __init__(
         self,
         paths: Dict,
         ehr_id: Dict,
-        set_missing_required_to_default: bool = True,
+        set_missing_required_to_default: bool = False,
     ):
         self._ehr_id = EhrId(set(ehr_id.get("maps_to", [])), ehr_id["value"])
         self._set_missing_required_to_default = set_missing_required_to_default
@@ -182,39 +182,39 @@ def build_composition(
 
     consumed_paths = []
     ehr_id_kvs = {}
-    for source_key, source_value in source_kvs:
-
-        if source_key in conf.ehr_id.maps_to:
-            ehr_id_kvs[source_key] = source_value
-
-        _paths = conf.inverse_mappings[source_key]
-        for path in _paths:
-            if "*" in path._id:
-                continue
-
-            if not path.suffixes:
-                composition.add(path._id)
-            else:
-                try:
-                    value_dicts = pending_value_dicts.pop((source_key, path._id))
-                except KeyError:
-                    value_dicts = [
-                        ValueDict(composition.template, path, path.value_map)
-                    ]
-
-                    for k in path.maps_to:
-                        if k != source_key:
-                            pending_value_dicts[(k, path._id)] += value_dicts
-
-                    if path._id.startswith("ctx/"):
-                        ctx[path._id] = value_dicts[0]
-                    else:
-                        composition[path._id] = value_dicts[0]
-
-                for vd in value_dicts:
-                    if source_value:
-                        vd.add_source_key_value(source_key, source_value)
-            consumed_paths.append(path)
+    for source_key, source_values in source_kvs:
+        for source_value in source_values:
+            if source_key in conf.ehr_id.maps_to:
+                ehr_id_kvs[source_key] = source_value
+
+            _paths = conf.inverse_mappings[source_key]
+            for path in _paths:
+                if "*" in path._id:
+                    continue
+
+                if not path.suffixes:
+                    composition.add(path._id)
+                else:
+                    try:
+                        value_dicts = pending_value_dicts.pop((source_key, path._id))
+                    except KeyError:
+                        value_dicts = [
+                            ValueDict(composition.template, path, path.value_map)
+                        ]
+
+                        for k in path.maps_to:
+                            if k != source_key:
+                                pending_value_dicts[(k, path._id)] += value_dicts
+
+                        if path._id.startswith("ctx/"):
+                            ctx[path._id] = value_dicts[0]
+                        else:
+                            composition[path._id] = value_dicts[0]
+
+                    for vd in value_dicts:
+                        if source_value:
+                            vd.add_source_key_value(source_key, source_value)
+                consumed_paths.append(path)
 
     for path in set([p for p in conf.paths if not p._id.startswith("ctx")]) - set(
         consumed_paths
@@ -245,7 +245,7 @@ def _get_conf(conf_file: str) -> Config:
         paths=conf_kwargs["paths"],
         ehr_id=conf_kwargs["ehr_id"],
         set_missing_required_to_default=conf_kwargs.get(
-            "set_missing_required_to_default", True
+            "set_missing_required_to_default", False
         ),
     )
 
diff --git a/flatehr/cli/generate.py b/flatehr/cli/generate.py
index cbd654c..a9fa00f 100644
--- a/flatehr/cli/generate.py
+++ b/flatehr/cli/generate.py
@@ -132,7 +132,7 @@ def conf_from_file(conf_file: str) -> Config:
         paths=conf_kwargs["paths"],
         ehr_id=conf_kwargs["ehr_id"],
         set_missing_required_to_default=conf_kwargs.get(
-            "set_missing_required_to_default", True
+            "set_missing_required_to_default", False
         ),
     )
 
diff --git a/flatehr/core.py b/flatehr/core.py
index 6363c9d..4d0ecf9 100644
--- a/flatehr/core.py
+++ b/flatehr/core.py
@@ -286,5 +286,6 @@ def flat(
     value_dicts.update(ctx or {})
     for _id, suffixes in value_dicts.items():
         for suffix, value in suffixes.items():
-            dct[_id + suffix] = value
+            if value:
+                dct[_id + suffix] = value
     return dct