diff --git a/sphinx/domains/c.py b/sphinx/domains/c.py
index e3570b593f6..5896f4a80cb 100644
--- a/sphinx/domains/c.py
+++ b/sphinx/domains/c.py
@@ -1533,6 +1533,7 @@ def _fill_empty(self, declaration: ASTDeclaration, docname: str, line: int) -> N
         self.declaration = declaration
         self.declaration.symbol = self
         self.docname = docname
+        self.line = line
         self._assert_invariants()
         # and symbol addition should be done as well
         self._add_function_params()