diff --git a/source/fuzz/fuzzer_pass_interchange_signedness_of_integer_operands.cpp b/source/fuzz/fuzzer_pass_interchange_signedness_of_integer_operands.cpp
index 6c3aa7b..0e40b49 100644
--- a/source/fuzz/fuzzer_pass_interchange_signedness_of_integer_operands.cpp
+++ b/source/fuzz/fuzzer_pass_interchange_signedness_of_integer_operands.cpp
@@ -91,6 +91,13 @@
 
 uint32_t FuzzerPassInterchangeSignednessOfIntegerOperands::
     FindOrCreateToggledIntegerConstant(uint32_t id) {
+  // |id| must not be a specialization constant because we do not know the value
+  // of specialization constants.
+  if (opt::IsSpecConstantInst(
+          GetIRContext()->get_def_use_mgr()->GetDef(id)->opcode())) {
+    return 0;
+  }
+
   auto constant = GetIRContext()->get_constant_mgr()->FindDeclaredConstant(id);
 
   // This pass only toggles integer constants.
diff --git a/source/fuzz/fuzzer_pass_interchange_zero_like_constants.cpp b/source/fuzz/fuzzer_pass_interchange_zero_like_constants.cpp
index 8bd670f..20575e1 100644
--- a/source/fuzz/fuzzer_pass_interchange_zero_like_constants.cpp
+++ b/source/fuzz/fuzzer_pass_interchange_zero_like_constants.cpp
@@ -34,6 +34,12 @@
 
 uint32_t FuzzerPassInterchangeZeroLikeConstants::FindOrCreateToggledConstant(
     opt::Instruction* declaration) {
+  // |declaration| must not be a specialization constant because we do not know
+  // the value of specialization constants.
+  if (opt::IsSpecConstantInst(declaration->opcode())) {
+    return 0;
+  }
+
   auto constant = GetIRContext()->get_constant_mgr()->FindDeclaredConstant(
       declaration->result_id());
 
@@ -107,4 +113,4 @@
   }
 }
 }  // namespace fuzz
-}  // namespace spvtools
\ No newline at end of file
+}  // namespace spvtools