diff --git a/src/api/environment.cc b/src/api/environment.cc
index e5d06f27d13110..eeeef7442d834a 100644
--- a/src/api/environment.cc
+++ b/src/api/environment.cc
@@ -1,4 +1,3 @@
-#include "env-inl.h"
 #include "node.h"
 #include "node_context_data.h"
 #include "node_errors.h"
diff --git a/src/api/utils.cc b/src/api/utils.cc
index 3e59932f2f8b73..da7281a68f3bb1 100644
--- a/src/api/utils.cc
+++ b/src/api/utils.cc
@@ -1,4 +1,3 @@
-#include "env-inl.h"
 #include "node.h"
 #include "node_internals.h"
 #include "util-inl.h"
diff --git a/src/diagnosticfilename-inl.h b/src/diagnosticfilename-inl.h
new file mode 100644
index 00000000000000..58a3a933acc605
--- /dev/null
+++ b/src/diagnosticfilename-inl.h
@@ -0,0 +1,33 @@
+#ifndef SRC_DIAGNOSTICFILENAME_INL_H_
+#define SRC_DIAGNOSTICFILENAME_INL_H_
+
+#if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
+
+#include "node_internals.h"
+#include "env-inl.h"
+
+namespace node {
+
+inline DiagnosticFilename::DiagnosticFilename(
+    Environment* env,
+    const char* prefix,
+    const char* ext) :
+  filename_(MakeFilename(env->thread_id(), prefix, ext)) {
+}
+
+inline DiagnosticFilename::DiagnosticFilename(
+    uint64_t thread_id,
+    const char* prefix,
+    const char* ext) :
+  filename_(MakeFilename(thread_id, prefix, ext)) {
+}
+
+inline const char* DiagnosticFilename::operator*() const {
+  return filename_.c_str();
+}
+
+}  // namespace node
+
+#endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
+
+#endif  // SRC_DIAGNOSTICFILENAME_INL_H_
diff --git a/src/heap_utils.cc b/src/heap_utils.cc
index acc63fd1d9a14c..8391f1de3726c1 100644
--- a/src/heap_utils.cc
+++ b/src/heap_utils.cc
@@ -1,3 +1,4 @@
+#include "diagnosticfilename-inl.h"
 #include "env-inl.h"
 #include "memory_tracker-inl.h"
 #include "stream_base-inl.h"
diff --git a/src/inspector/tracing_agent.cc b/src/inspector/tracing_agent.cc
index d87eec6a6469b9..609d70d22f843c 100644
--- a/src/inspector/tracing_agent.cc
+++ b/src/inspector/tracing_agent.cc
@@ -2,9 +2,6 @@
 #include "main_thread_interface.h"
 #include "node_internals.h"
 #include "node_v8_platform-inl.h"
-
-#include "env-inl.h"
-#include "util-inl.h"
 #include "v8.h"
 
 #include <set>
diff --git a/src/inspector_io.cc b/src/inspector_io.cc
index 7ba19087d01b0d..223e3592a1fc09 100644
--- a/src/inspector_io.cc
+++ b/src/inspector_io.cc
@@ -4,7 +4,6 @@
 #include "inspector/main_thread_interface.h"
 #include "inspector/node_string.h"
 #include "base_object-inl.h"
-#include "env-inl.h"
 #include "debug_utils.h"
 #include "node.h"
 #include "node_crypto.h"
diff --git a/src/inspector_profiler.cc b/src/inspector_profiler.cc
index 7e76ad778a0f4a..2a1559f8f97495 100644
--- a/src/inspector_profiler.cc
+++ b/src/inspector_profiler.cc
@@ -2,6 +2,7 @@
 #include <sstream>
 #include "base_object-inl.h"
 #include "debug_utils.h"
+#include "diagnosticfilename-inl.h"
 #include "memory_tracker-inl.h"
 #include "node_file.h"
 #include "node_internals.h"
diff --git a/src/node_api.cc b/src/node_api.cc
index 32393883d7c601..91e6a14cdc1570 100644
--- a/src/node_api.cc
+++ b/src/node_api.cc
@@ -1,9 +1,9 @@
-#include <node_buffer.h>
 #include "env-inl.h"
 #define NAPI_EXPERIMENTAL
 #include "js_native_api_v8.h"
 #include "node_api.h"
 #include "node_binding.h"
+#include "node_buffer.h"
 #include "node_errors.h"
 #include "node_internals.h"
 #include "threadpoolwork-inl.h"
diff --git a/src/node_i18n.cc b/src/node_i18n.cc
index 0c565c447fb862..8ccda35056c342 100644
--- a/src/node_i18n.cc
+++ b/src/node_i18n.cc
@@ -45,7 +45,6 @@
 #if defined(NODE_HAVE_I18N_SUPPORT)
 
 #include "base_object-inl.h"
-#include "env-inl.h"
 #include "node.h"
 #include "node_buffer.h"
 #include "node_errors.h"
diff --git a/src/node_internals.h b/src/node_internals.h
index 8e6734192cbded..21625e60232bbe 100644
--- a/src/node_internals.h
+++ b/src/node_internals.h
@@ -324,17 +324,15 @@ class DiagnosticFilename {
  public:
   static void LocalTime(TIME_TYPE* tm_struct);
 
-  DiagnosticFilename(Environment* env,
-                     const char* prefix,
-                     const char* ext) :
-      filename_(MakeFilename(env->thread_id(), prefix, ext)) {}
+  inline DiagnosticFilename(Environment* env,
+                            const char* prefix,
+                            const char* ext);
 
-  DiagnosticFilename(uint64_t thread_id,
-                     const char* prefix,
-                     const char* ext) :
-      filename_(MakeFilename(thread_id, prefix, ext)) {}
+  inline DiagnosticFilename(uint64_t thread_id,
+                            const char* prefix,
+                            const char* ext);
 
-  const char* operator*() const { return filename_.c_str(); }
+  inline const char* operator*() const;
 
  private:
   static std::string MakeFilename(
diff --git a/src/node_report.cc b/src/node_report.cc
index 2f668b54630761..18607656256d51 100644
--- a/src/node_report.cc
+++ b/src/node_report.cc
@@ -1,6 +1,7 @@
 #include "env-inl.h"
 #include "node_report.h"
 #include "debug_utils.h"
+#include "diagnosticfilename-inl.h"
 #include "node_internals.h"
 #include "node_metadata.h"
 #include "util.h"
diff --git a/src/node_report_utils.cc b/src/node_report_utils.cc
index 2581af06fac62d..33d7c52b34f78e 100644
--- a/src/node_report_utils.cc
+++ b/src/node_report_utils.cc
@@ -1,4 +1,3 @@
-#include "env-inl.h"
 #include "node_internals.h"
 #include "node_report.h"
 #include "util-inl.h"
diff --git a/src/node_trace_events.cc b/src/node_trace_events.cc
index 24e1d66fb7e7f4..f5852076b4ec68 100644
--- a/src/node_trace_events.cc
+++ b/src/node_trace_events.cc
@@ -1,5 +1,5 @@
 #include "base_object-inl.h"
-#include "env.h"
+#include "env-inl.h"
 #include "memory_tracker-inl.h"
 #include "node.h"
 #include "node_internals.h"
diff --git a/tools/snapshot/node_mksnapshot.cc b/tools/snapshot/node_mksnapshot.cc
index 5cf24f32b49e01..f52cccb705f53a 100644
--- a/tools/snapshot/node_mksnapshot.cc
+++ b/tools/snapshot/node_mksnapshot.cc
@@ -5,7 +5,6 @@
 #include <string>
 #include <vector>
 
-#include "env-inl.h"
 #include "libplatform/libplatform.h"
 #include "node_internals.h"
 #include "snapshot_builder.h"
diff --git a/tools/snapshot/snapshot_builder.cc b/tools/snapshot/snapshot_builder.cc
index 1faa5330ae118f..54a4a2e73da249 100644
--- a/tools/snapshot/snapshot_builder.cc
+++ b/tools/snapshot/snapshot_builder.cc
@@ -1,7 +1,6 @@
 #include "snapshot_builder.h"
 #include <iostream>
 #include <sstream>
-#include "env-inl.h"
 #include "node_internals.h"
 #include "node_main_instance.h"
 #include "node_v8_platform-inl.h"