diff --git a/frictionless/detector/detector.py b/frictionless/detector/detector.py
index 1938913b9c..dbf4fde8a6 100644
--- a/frictionless/detector/detector.py
+++ b/frictionless/detector/detector.py
@@ -298,6 +298,7 @@ def detect_schema(
         labels: Optional[List[str]] = None,
         schema: Optional[Schema] = None,
         field_candidates: List[Dict[str, Any]] = settings.DEFAULT_FIELD_CANDIDATES,
+        **options: Any,
     ) -> Schema:
         """Detect schema from fragment
 
@@ -419,9 +420,10 @@ def detect_schema(
                 for _, field in mapping.items():
                     if field and field.required and field.name not in labels:
                         schema.add_field(field)
-                    # For primary field that are missing
-                    if field and not field.required and field.name in schema.primary_key and field.name not in labels:
-                        schema.add_field(field)
+                    # For primary key field that are missing
+                    self.add_missing_primary_key_to_schema_fields(
+                        field, schema, labels, options["header_case"]  # type: ignore
+                    )
 
         # Patch schema
         if self.schema_patch:
@@ -436,3 +438,27 @@ def detect_schema(
             schema = Schema.from_descriptor(descriptor)
 
         return schema  # type: ignore
+
+    @staticmethod
+    def add_missing_primary_key_to_schema_fields(
+        field: Field,
+        schema: Schema,
+        labels: List[str],
+        case_sensitive: bool,
+    ):
+        if case_sensitive:
+            if (
+                not field.required
+                and field.name in schema.primary_key
+                and field.name not in labels
+            ):
+                schema.add_field(field)
+        else:
+            lower_primary_key = [pk.lower() for pk in schema.primary_key]
+            lower_labels = [label.lower() for label in labels]
+            if (
+                not field.required
+                and field.name.lower() in lower_primary_key
+                and field.name.lower() not in lower_labels
+            ):
+                schema.add_field(field)
diff --git a/frictionless/resources/table.py b/frictionless/resources/table.py
index 8a8882bf95..0b547a3a09 100644
--- a/frictionless/resources/table.py
+++ b/frictionless/resources/table.py
@@ -204,6 +204,7 @@ def __open_schema(self):
             labels=self.labels,
             schema=self.schema,
             field_candidates=system.detect_field_candidates(),
+            header_case=self.dialect.header_case,
         )
         self.stats.fields = len(self.schema.fields)
 
@@ -303,7 +304,6 @@ def __open_row_stream(self):
         enumerated_content_stream = self.dialect.read_enumerated_content_stream(
             self.cell_stream
         )
-        
 
         # Create row stream
         def row_stream():
@@ -333,8 +333,7 @@ def row_stream():
                 # Primary Key Error
                 if is_integrity and self.schema.primary_key:
                     try:
-                        cells = self.primary_key_cells(row,
-                                                       self.dialect.header_case)
+                        cells = self.primary_key_cells(row, self.dialect.header_case)
                     except KeyError:
                         # Row does not have primary_key as key
                         # There should already be a missing-label error in
@@ -409,16 +408,13 @@ def row_stream():
         # # Create row stream
         self.__row_stream = row_stream()
 
-    def primary_key_cells(
-        self,
-        row: Row,
-        case_sensitive: bool
-    ) -> Tuple[str, Any]:
-        """Create a tuple containg all cells related to primary_key
-        """
-        return tuple(row[label] for label in
-                     self.labels_related_to_primary_key(row, case_sensitive))
-    
+    def primary_key_cells(self, row: Row, case_sensitive: bool) -> Tuple[str, Any]:
+        """Create a tuple containg all cells related to primary_key"""
+        return tuple(
+            row[label]
+            for label in self.labels_related_to_primary_key(row, case_sensitive)
+        )
+
     def labels_related_to_primary_key(
         self,
         row: Row,
@@ -430,11 +426,10 @@ def labels_related_to_primary_key(
         if case_sensitive:
             labels_primary_key = self.schema.primary_key
         else:
-            lower_primary_key = [
-                pk.lower() for pk in self.schema.primary_key
+            lower_primary_key = [pk.lower() for pk in self.schema.primary_key]
+            labels_primary_key = [
+                label for label in row.field_names if label.lower() in lower_primary_key
             ]
-            labels_primary_key = [label for label in row.field_names
-                                  if label.lower() in lower_primary_key]
         return labels_primary_key
 
     # Read
diff --git a/tests/table/test_header.py b/tests/table/test_header.py
index 7caad5b424..7583e84517 100644
--- a/tests/table/test_header.py
+++ b/tests/table/test_header.py
@@ -78,7 +78,7 @@ def test_missing_primary_key_label_with_shema_sync_issue_1633():
     # Ignore header_case
     schema_descriptor = {
         "$schema": "https://frictionlessdata.io/schemas/table-schema.json",
-        "fields": [{"name": "A", "constraints": {"required": True}}],
+        "fields": [{"name": "A"}],
         "primaryKey": ["A"],
     }