diff --git a/src/libutil/error.cc b/src/libutil/error.cc
index 5384248f8..2b7a079dc 100644
--- a/src/libutil/error.cc
+++ b/src/libutil/error.cc
@@ -5,11 +5,7 @@
 
 namespace nix {
 
-using std::cout;
-using std::endl;
-using std::nullopt;
-
-optional<string> ErrorInfo::programName = nullopt;
+optional<string> ErrorInfo::programName = std::nullopt;
 
 // return basic_format?
 string showErrLine(ErrLine &errLine)
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index 00539f06a..614f08a35 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -1,4 +1,5 @@
-#pragma once
+#ifndef error_hh
+#define error_hh
 
 #include "ansicolor.hh"
 #include <string>
@@ -8,12 +9,6 @@
 
 #include <boost/format.hpp>
 
-using std::string;
-using std::optional;
-using boost::format;
-using std::cout;
-using std::endl;
-
 namespace nix {
 
 typedef enum  
@@ -36,7 +31,6 @@ class ErrLine {
     optional<string> prevLineOfCode;
     string errLineOfCode;
     optional<string> nextLineOfCode;
-
 };
 
 class NixCode { 
@@ -112,8 +106,6 @@ class ErrorInfo {
   protected:
     // constructor is protected, so only the builder classes can create an ErrorInfo.
     ErrorInfo(ErrLevel level) { this->level = level; }
-
-
 };
 
 // Init as error
@@ -285,7 +277,9 @@ typedef AddName<
 // --------------------------------------------------------
 // error printing
 
+// just to cout for now.
 void printErrorInfo(ErrorInfo &einfo);
 
 }
 
+#endif
diff --git a/tests/errors/main.cc b/tests/errors/main.cc
index 9d08e82ea..f11390c73 100644
--- a/tests/errors/main.cc
+++ b/tests/errors/main.cc
@@ -3,95 +3,91 @@
 #include <optional>
 #include <iostream>
 
-using std::optional;
-using std::nullopt;
-using std::cout;
-using std::endl;
 
 
 int main() 
 {
-  using namespace nix; 
+    using namespace nix; 
 
-  // In each program where errors occur, this has to be set.
-  ErrorInfo::programName = optional("error-test");
+    // In each program where errors occur, this has to be set.
+    ErrorInfo::programName = optional("error-test");
 
-  // There are currently four error types:
-  //  
-  // 			ProgramError, ProgramWarning, NixLangError, NixLangWarning.
-  // 			
-  // Each error type is created with a specific sequence of builder functions.
-  // Unlike with a constructor, each parameter is clearly named.
-  // If the sequence of function calls isn't followed, then there's a type error.
-  // This should make for a consistent look in the code when errors are created.
+    // There are currently four error types:
+    //  
+    // 			ProgramError, ProgramWarning, NixLangError, NixLangWarning.
+    // 			
+    // Each error type is created with a specific sequence of builder functions.
+    // Unlike with a constructor, each parameter is clearly named.
+    // If the sequence of function calls isn't followed, then there's a type error.
+    // This should make for a consistent look in the code when errors are created.
 
-  // ProgramError takes name, description, and an optional hint.
-  printErrorInfo(
-    ProgramError()
-      .name("name")
-      .description("error description")
-      .nohint()
-      );
+    // ProgramError takes name, description, and an optional hint.
+    printErrorInfo(
+        ProgramError()
+            .name("name")
+            .description("error description")
+            .nohint()
+            );
 
-  // ProgramWarning takes name, description, and an optional hint.
-  // The hint is in the form of a hintfmt class, which wraps boost::format(), and 
-  // makes all the substituted text yellow.
-  printErrorInfo(
-    ProgramWarning()
-      .name("warning name")
-      .description("warning description")
-      .hint(hintfmt("there was a %1%") % "warning") // 'warning' will be yellow.
-      );
+    // ProgramWarning takes name, description, and an optional hint.
+    // The hint is in the form of a hintfmt class, which wraps boost::format(), and 
+    // makes all the substituted text yellow.
+    printErrorInfo(
+        ProgramWarning()
+            .name("warning name")
+            .description("warning description")
+            .hint(hintfmt("there was a %1%") % "warning") // 'warning' will be yellow.
+            );
 
-  /*
-    // some invalid errors:
-    
-    // type error: no hint function.
-    ProgramError()
-      .name("name")
-      .description("error description");
+    /*
+      // some invalid errors:
+      
+      // type error: no hint function.
+      ProgramError()
+        .name("name")
+        .description("error description");
 
-    // type error:  description before name.
-    ProgramError()
-      .description("error description")
-      .name("name")
-      .nohint();
+      // type error:  description before name.
+      ProgramError()
+        .description("error description")
+        .name("name")
+        .nohint();
 
-    // type error: hint function with regular boost format, not special hintfmt.
-    ProgramError()
-      .description("error description")
-      .name("name")
-      .hint(format("there was a %1%") % "warning");
-  */
+      // type error: hint function with regular boost format, not special hintfmt.
+      ProgramError()
+        .description("error description")
+        .name("name")
+        .hint(format("there was a %1%") % "warning");
+    */
 
-  // NixLangWarning adds nix file, line number, column range, and the lines of code 
-  // where a warning occurred.
-  printErrorInfo(
-    NixLangWarning()
-      .name("warning name")
-      .description("warning description")
-      .nixFile("myfile.nix")
-      .lineNumber(40)
-      .columnRange(13,7)
-      .linesOfCode(nullopt
-                  ,"this is the problem line of code"
-                  ,nullopt)
-      .hint(hintfmt("this hint has %1% templated %2%!!") % "yellow" % "values")
-      );
+    // NixLangWarning adds nix file, line number, column range, and the lines of code 
+    // where a warning occurred.
+    printErrorInfo(
+        NixLangWarning()
+            .name("warning name")
+            .description("warning description")
+            .nixFile("myfile.nix")
+            .lineNumber(40)
+            .columnRange(13,7)
+            .linesOfCode(std::nullopt
+                        ,"this is the problem line of code"
+                        ,std::nullopt)
+            .hint(hintfmt("this hint has %1% templated %2%!!") % "yellow" % "values")
+            );
 
-  // NixLangError is just the same as NixLangWarning, except for the Error flag.
-  printErrorInfo(
-    NixLangError()
-      .name("error name")
-      .description("error description")
-      .nixFile("myfile.nix")
-      .lineNumber(40)
-      .columnRange(13,7)
-      .linesOfCode(optional("previous line of code")
-                  ,"this is the problem line of code"
-                  ,optional("next line of code"))
-      .hint(hintfmt("this hint has %1% templated %2%!!") % "yellow" % "values")
-      );
+    // NixLangError is just the same as NixLangWarning, except for the Error flag.
+    printErrorInfo(
+        NixLangError()
+            .name("error name")
+            .description("error description")
+            .nixFile("myfile.nix")
+            .lineNumber(40)
+            .columnRange(13,7)
+            .linesOfCode(optional("previous line of code")
+                        ,"this is the problem line of code"
+                        ,optional("next line of code"))
+            .hint(hintfmt("this hint has %1% templated %2%!!") % "yellow" % "values")
+            );
 
-  return 0;
+    return 0;
 }