diff --git a/src/inspector/inspector_test.cc b/src/inspector/inspector_test.cc
index 00bc302b39..2dddfbeec0 100644
--- a/src/inspector/inspector_test.cc
+++ b/src/inspector/inspector_test.cc
@@ -18,6 +18,7 @@
 #include "src/ast/stage_decoration.h"
 #include "src/ast/struct_block_decoration.h"
 #include "src/ast/workgroup_decoration.h"
+#include "src/program_builder.h"
 #include "src/sem/depth_texture_type.h"
 #include "src/sem/external_texture_type.h"
 #include "src/sem/multisampled_texture_type.h"
diff --git a/src/program_builder.h b/src/program_builder.h
index 55995b54ba..8a38e182f6 100644
--- a/src/program_builder.h
+++ b/src/program_builder.h
@@ -78,6 +78,10 @@
 #include "src/sem/vector_type.h"
 #include "src/sem/void_type.h"
 
+#ifdef INCLUDE_TINT_TINT_H_
+#error "internal tint header being #included from tint.h"
+#endif
+
 namespace tint {
 
 // Forward declarations
diff --git a/src/writer/hlsl/generator.cc b/src/writer/hlsl/generator.cc
index 7fdc28ab4f..d55e70c814 100644
--- a/src/writer/hlsl/generator.cc
+++ b/src/writer/hlsl/generator.cc
@@ -14,6 +14,8 @@
 
 #include "src/writer/hlsl/generator.h"
 
+#include "src/writer/hlsl/generator_impl.h"
+
 namespace tint {
 namespace writer {
 namespace hlsl {
diff --git a/src/writer/hlsl/generator.h b/src/writer/hlsl/generator.h
index 614a62daf3..3623dd59d9 100644
--- a/src/writer/hlsl/generator.h
+++ b/src/writer/hlsl/generator.h
@@ -18,13 +18,15 @@
 #include <memory>
 #include <string>
 
-#include "src/writer/hlsl/generator_impl.h"
 #include "src/writer/text.h"
 
 namespace tint {
 namespace writer {
 namespace hlsl {
 
+// Forward declarations
+class GeneratorImpl;
+
 /// Class to generate HLSL source
 class Generator : public Text {
  public:
diff --git a/src/writer/spirv/generator.cc b/src/writer/spirv/generator.cc
index d000b11548..8a1e5980e1 100644
--- a/src/writer/spirv/generator.cc
+++ b/src/writer/spirv/generator.cc
@@ -14,6 +14,8 @@
 
 #include "src/writer/spirv/generator.h"
 
+#include "src/writer/spirv/binary_writer.h"
+
 namespace tint {
 namespace writer {
 namespace spirv {
@@ -35,6 +37,10 @@ bool Generator::Generate() {
   return true;
 }
 
+const std::vector<uint32_t>& Generator::result() const {
+  return writer_->result();
+}
+
 }  // namespace spirv
 }  // namespace writer
 }  // namespace tint
diff --git a/src/writer/spirv/generator.h b/src/writer/spirv/generator.h
index b5b1614474..5227a3f499 100644
--- a/src/writer/spirv/generator.h
+++ b/src/writer/spirv/generator.h
@@ -19,13 +19,16 @@
 #include <string>
 #include <vector>
 
-#include "src/writer/spirv/binary_writer.h"
 #include "src/writer/writer.h"
 
 namespace tint {
 namespace writer {
 namespace spirv {
 
+/// Forward declarations
+class Builder;
+class BinaryWriter;
+
 /// Class to generate SPIR-V from a Tint program
 class Generator : public writer::Writer {
  public:
@@ -41,7 +44,7 @@ class Generator : public writer::Writer {
   bool Generate() override;
 
   /// @returns the result data
-  const std::vector<uint32_t>& result() const { return writer_->result(); }
+  const std::vector<uint32_t>& result() const;
 
  private:
   std::unique_ptr<Builder> builder_;