diff --git a/data_prep/introspector.py b/data_prep/introspector.py
index 61d7e9f288..052a12377d 100755
--- a/data_prep/introspector.py
+++ b/data_prep/introspector.py
@@ -49,6 +49,7 @@
 INTROSPECTOR_TYPE = ''
 INTROSPECTOR_FUNC_SIG = ''
 INTROSPECTOR_ADDR_TYPE = ''
+INTROSPECTOR_ALL_HEADER_FILES = ''
 
 
 def get_oracle_dict() -> Dict[str, Any]:
@@ -66,7 +67,8 @@ def set_introspector_endpoints(endpoint):
   global INTROSPECTOR_ENDPOINT, INTROSPECTOR_CFG, INTROSPECTOR_FUNC_SIG, \
       INTROSPECTOR_FUNCTION_SOURCE, INTROSPECTOR_PROJECT_SOURCE, \
       INTROSPECTOR_XREF, INTROSPECTOR_TYPE, INTROSPECTOR_ORACLE_FAR_REACH, \
-      INTROSPECTOR_ORACLE_KEYWORD, INTROSPECTOR_ADDR_TYPE
+      INTROSPECTOR_ORACLE_KEYWORD, INTROSPECTOR_ADDR_TYPE, \
+      INTROSPECTOR_ALL_HEADER_FILES
 
   INTROSPECTOR_ENDPOINT = endpoint
   logging.info('Fuzz Introspector endpoint set to %s', INTROSPECTOR_ENDPOINT)
@@ -83,6 +85,7 @@ def set_introspector_endpoints(endpoint):
   INTROSPECTOR_FUNC_SIG = f'{INTROSPECTOR_ENDPOINT}/function-signature'
   INTROSPECTOR_ADDR_TYPE = (
       f'{INTROSPECTOR_ENDPOINT}/addr-to-recursive-dwarf-info')
+  INTROSPECTOR_ALL_HEADER_FILES = (f'{INTROSPECTOR_ENDPOINT}/all-header-files')
 
 
 def _construct_url(api: str, params: dict) -> str:
@@ -182,6 +185,13 @@ def query_introspector_cfg(project: str) -> dict:
   return _get_data(resp, 'project', {})
 
 
+def query_introspector_header_files(project: str) -> List[str]:
+  resp = _query_introspector(INTROSPECTOR_ALL_HEADER_FILES,
+                             {'project': project})
+  all_header_files = _get_data(resp, 'all-header-files', [])
+  return all_header_files
+
+
 def query_introspector_function_source(project: str, func_sig: str) -> str:
   """Queries FuzzIntrospector API for source code of |func_sig|."""
   resp = _query_introspector(INTROSPECTOR_FUNCTION_SOURCE, {
diff --git a/llm_toolkit/prompt_builder.py b/llm_toolkit/prompt_builder.py
index 8cb0aa1b59..6a183cc9ca 100644
--- a/llm_toolkit/prompt_builder.py
+++ b/llm_toolkit/prompt_builder.py
@@ -24,7 +24,7 @@
 import requests
 import yaml
 
-from data_prep import project_targets
+from data_prep import introspector, project_targets
 from experiment.benchmark import Benchmark, FileType
 from experiment.fuzz_target_error import SemanticCheckResult
 from llm_toolkit import models, prompts
@@ -46,6 +46,7 @@
                                          'jansi_colors-problem.txt')
 FDP_JVM_EXAMPLE_2_SOLUTION = os.path.join(EXAMPLE_PATH,
                                           'jansi_colors-solution.java')
+HEADER_FIXER_PROMPT = os.path.join(DEFAULT_TEMPLATE_DIR, 'header_fixer.txt')
 
 EXAMPLES = {
     'c++': [
@@ -271,7 +272,7 @@ def build_fixer_prompt(self, benchmark: Benchmark, raw_code: str,
     """Prepares the code-fixing prompt."""
     priming, priming_weight = self._format_fixer_priming()
     problem = self._format_fixer_problem(raw_code, error_desc, errors,
-                                         priming_weight)
+                                         priming_weight, benchmark)
 
     self._prepare_prompt(priming, problem)
     return self._prompt
@@ -287,7 +288,8 @@ def _format_fixer_priming(self) -> Tuple[str, int]:
     return priming, priming_weight
 
   def _format_fixer_problem(self, raw_code: str, error_desc: Optional[str],
-                            errors: list[str], priming_weight: int) -> str:
+                            errors: list[str], priming_weight: int,
+                            benchmark: Benchmark) -> str:
     """Formats a problem for code fixer based on the template."""
     with open(self.fixer_problem_template_file) as f:
       problem = f.read().strip()
@@ -297,6 +299,17 @@ def _format_fixer_problem(self, raw_code: str, error_desc: Optional[str],
     else:
       # Build error does not pass error desc.
       error_summary = BUILD_ERROR_SUMMARY
+    headers_to_avoid = introspector.query_introspector_header_files(
+        benchmark.project)
+    if len(headers_to_avoid) > 0:
+      with open(HEADER_FIXER_PROMPT, 'r') as f:
+        header_avoid_string = f.read()
+      for header_file in headers_to_avoid:
+        header_avoid_string += '- %s\n' % (os.path.basename(header_file))
+    else:
+      header_avoid_string = ''
+    problem = problem.replace('{ADDITIONAL_MESSAGE}', header_avoid_string)
+
     problem = problem.replace('{ERROR_SUMMARY}', error_summary)
 
     problem_prompt = self._prompt.create_prompt_piece(problem, 'user')
diff --git a/prompts/template_xml/fixer_problem.txt b/prompts/template_xml/fixer_problem.txt
index 83663bf146..135dce96d5 100644
--- a/prompts/template_xml/fixer_problem.txt
+++ b/prompts/template_xml/fixer_problem.txt
@@ -13,4 +13,5 @@ Fix code:
 2. Choose a solution that can maximize fuzzing result, which is utilizing the function under test and feeding it not null input.
 3. Apply the solutions to the original code.
 It's important to show the complete code, not only the fixed line.
-<solution>
\ No newline at end of file
+{ADDITIONAL_MESSAGE}
+<solution>