diff --git a/src/common/windows/pdb_source_line_writer.cc b/src/common/windows/pdb_source_line_writer.cc
index 2fff67b0..0392627f 100644
--- a/src/common/windows/pdb_source_line_writer.cc
+++ b/src/common/windows/pdb_source_line_writer.cc
@@ -615,7 +615,8 @@ int PDBSourceLineWriter::GetFunctionStackParamSize(IDiaSymbol *function) {
       goto next_child;
     }
 
-    if (FAILED(child->get_type(&child_type))) {
+    // IDiaSymbol::get_type can succeed but still pass back a NULL value.
+    if (FAILED(child->get_type(&child_type)) || !child_type) {
       goto next_child;
     }