diff --git a/src/FGJSBBase.cpp b/src/FGJSBBase.cpp
index f1c6213912..30b39688be 100644
--- a/src/FGJSBBase.cpp
+++ b/src/FGJSBBase.cpp
@@ -35,8 +35,6 @@ HISTORY
 INCLUDES
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
-#define BASE
-
 #include "FGJSBBase.h"
 #include "models/FGAtmosphere.h"
 
diff --git a/src/input_output/FGXMLElement.cpp b/src/input_output/FGXMLElement.cpp
index c7154287b0..5ac3697e93 100644
--- a/src/input_output/FGXMLElement.cpp
+++ b/src/input_output/FGXMLElement.cpp
@@ -28,6 +28,7 @@
 INCLUDES
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
+#include <iostream>
 #include <sstream>  // for assembling the error messages / what of exceptions.
 #include <stdexcept>  // using domain_error, invalid_argument, and length_error.
 #include "FGXMLElement.h"
diff --git a/src/input_output/FGfdmSocket.cpp b/src/input_output/FGfdmSocket.cpp
index ced3a16c0b..5034068912 100644
--- a/src/input_output/FGfdmSocket.cpp
+++ b/src/input_output/FGfdmSocket.cpp
@@ -51,6 +51,8 @@ INCLUDES
 #include <unistd.h>
 #endif
 #include <iomanip>
+#include <iostream>
+#include <sstream>
 #include <cstring>
 #include "FGfdmSocket.h"
 
diff --git a/src/input_output/string_utilities.cpp b/src/input_output/string_utilities.cpp
index 1d4fbd0eca..2031e9dcbe 100644
--- a/src/input_output/string_utilities.cpp
+++ b/src/input_output/string_utilities.cpp
@@ -35,12 +35,14 @@ INCLUDES
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
 #include <errno.h>
+#include <iostream>
+#include <sstream>
+#include <stdio.h>
 #ifdef __APPLE__
 #include <xlocale.h>
 #else
 #include <locale.h>
 #endif
-#include <sstream>
 
 #include "FGJSBBase.h"
 #include "string_utilities.h"
@@ -51,6 +53,7 @@ typedef _locale_t locale_t;
 #define strtod_l _strtod_l
 #endif
 
+namespace JSBSim {
 struct CNumericLocale
 {
   CNumericLocale()
@@ -100,3 +103,92 @@ double atof_locale_c(const std::string& input)
   std::cerr << s.str() << std::endl;
   throw JSBSim::BaseException(s.str());
 }
+
+
+std::string& trim_left(std::string& str)
+{
+  while (!str.empty() && isspace((unsigned char)str[0])) {
+    str = str.erase(0,1);
+  }
+  return str;
+}
+
+std::string& trim_right(std::string& str)
+{
+  while (!str.empty() && isspace((unsigned char)str[str.size()-1])) {
+    str = str.erase(str.size()-1,1);
+  }
+  return str;
+}
+
+std::string& trim(std::string& str)
+{
+  if (str.empty()) return str;
+  std::string temp_str = trim_right(str);
+  return str = trim_left(temp_str);
+}
+
+std::string& trim_all_space(std::string& str)
+{
+  for (size_t i=0; i<str.size(); i++) {
+    if (isspace((unsigned char)str[i])) {
+      str = str.erase(i,1);
+      --i;
+    }
+  }
+  return str;
+}
+
+std::string& to_upper(std::string& str)
+{
+  for (size_t i=0; i<str.size(); i++) str[i] = toupper(str[i]);
+  return str;
+}
+
+std::string& to_lower(std::string& str)
+{
+  for (size_t i=0; i<str.size(); i++) str[i] = tolower(str[i]);
+  return str;
+}
+
+bool is_number(const std::string& str)
+{
+  if (str.empty())
+    return false;
+  else
+    return (str.find_first_not_of("+-.0123456789Ee") == std::string::npos);
+}
+
+std::vector <std::string> split(std::string str, char d)
+{
+  std::vector <std::string> str_array;
+  size_t index=0;
+  std::string temp = "";
+
+  trim(str);
+  index = str.find(d);
+  while (index != std::string::npos) {
+    temp = str.substr(0,index);
+    trim(temp);
+    if (!temp.empty()) str_array.push_back(temp);
+    str = str.erase(0,index+1);
+    index = str.find(d);
+  }
+  if (!str.empty()) {
+    temp = trim(str);
+    if (!temp.empty()) str_array.push_back(temp);
+  }
+
+  return str_array;
+}
+
+std::string replace(std::string str, const std::string& oldstr, const std::string& newstr)
+{
+  std::string temp = str;
+  size_t old_idx = str.find(oldstr);
+  if (old_idx != std::string::npos) {
+    temp = str.replace(old_idx, 1, newstr);
+  }
+  return temp;
+}
+};
diff --git a/src/input_output/string_utilities.h b/src/input_output/string_utilities.h
index 005dd2b496..8583ef6355 100644
--- a/src/input_output/string_utilities.h
+++ b/src/input_output/string_utilities.h
@@ -39,121 +39,24 @@ INCLUDES
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
 #include <string>
-#include <sstream>
-#include <iostream>
 #include <vector>
-#include <stdio.h>
-
-#include "JSBSim_API.h"
 
 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 CLASS DECLARATION
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
-JSBSIM_API bool is_number(const std::string& str);
+namespace JSBSim {
 JSBSIM_API double atof_locale_c(const std::string& input);
-
-#if !defined(BASE)
-  extern std::string& trim_left(std::string& str);
-  extern std::string& trim_right(std::string& str);
-  extern std::string& trim(std::string& str);
-  extern std::string& trim_all_space(std::string& str);
-  extern std::string& to_upper(std::string& str);
-  extern std::string& to_lower(std::string& str);
-  std::vector <std::string> split(std::string str, char d);
-
-  extern std::string replace(std::string str, const std::string& old, const std::string& newstr);
-#else
-  #include <cctype>
-
-  std::string& trim_left(std::string& str)
-  {
-    while (!str.empty() && isspace((unsigned char)str[0])) {
-      str = str.erase(0,1);
-    }
-    return str;
-  }
-
-  std::string& trim_right(std::string& str)
-  {
-    while (!str.empty() && isspace((unsigned char)str[str.size()-1])) {
-      str = str.erase(str.size()-1,1);
-    }
-    return str;
-  }
-
-  std::string& trim(std::string& str)
-  {
-    if (str.empty()) return str;
-    std::string temp_str = trim_right(str);
-    return str = trim_left(temp_str);
-  }
-
-  std::string& trim_all_space(std::string& str)
-  {
-    for (size_t i=0; i<str.size(); i++) {
-      if (isspace((unsigned char)str[i])) {
-        str = str.erase(i,1);
-        --i;
-      }
-    }
-    return str;
-  }
-
-  std::string& to_upper(std::string& str)
-  {
-    for (size_t i=0; i<str.size(); i++) str[i] = toupper(str[i]);
-    return str;
-  }
-
-  std::string& to_lower(std::string& str)
-  {
-    for (size_t i=0; i<str.size(); i++) str[i] = tolower(str[i]);
-    return str;
-  }
-
-  bool is_number(const std::string& str)
-  {
-    if (str.empty())
-      return false;
-    else
-      return (str.find_first_not_of("+-.0123456789Ee") == std::string::npos);
-  }
-
-  std::vector <std::string> split(std::string str, char d)
-  {
-    std::vector <std::string> str_array;
-    size_t index=0;
-    std::string temp = "";
-
-    trim(str);
-    index = str.find(d);
-    while (index != std::string::npos) {
-      temp = str.substr(0,index);
-      trim(temp);
-      if (!temp.empty()) str_array.push_back(temp);
-      str = str.erase(0,index+1);
-      index = str.find(d);
-    }
-    if (!str.empty()) {
-      temp = trim(str);
-      if (!temp.empty()) str_array.push_back(temp);
-    }
-
-    return str_array;
-  }
-
-  std::string replace(std::string str, const std::string& oldstr, const std::string& newstr)
-  {
-    std::string temp = str;
-    size_t old_idx = str.find(oldstr);
-    if (old_idx != std::string::npos) {
-      temp = str.replace(old_idx, 1, newstr);
-    }
-    return temp;
-  }
-
-#endif
+JSBSIM_API std::string& trim_left(std::string& str);
+JSBSIM_API std::string& trim_right(std::string& str);
+JSBSIM_API std::string& trim(std::string& str);
+JSBSIM_API std::string& trim_all_space(std::string& str);
+JSBSIM_API std::string& to_upper(std::string& str);
+JSBSIM_API std::string& to_lower(std::string& str);
+JSBSIM_API bool is_number(const std::string& str);
+JSBSIM_API std::vector <std::string> split(std::string str, char d);
+JSBSIM_API std::string replace(std::string str, const std::string& old, const std::string& newstr);
+};
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
diff --git a/src/simgear/xml/easyxml.cxx b/src/simgear/xml/easyxml.cxx
index 1b5725ffd4..3700bf24fd 100644
--- a/src/simgear/xml/easyxml.cxx
+++ b/src/simgear/xml/easyxml.cxx
@@ -23,6 +23,7 @@ INCLUDES
 
 #include <fstream>
 #include <iostream>
+#include <sstream>
 
 #include "FGJSBBase.h"
 
diff --git a/tests/unit_tests/StringUtilitiesTest.h b/tests/unit_tests/StringUtilitiesTest.h
index c82817f8ac..287cd167b4 100644
--- a/tests/unit_tests/StringUtilitiesTest.h
+++ b/tests/unit_tests/StringUtilitiesTest.h
@@ -1,9 +1,9 @@
 #include <string>
 #include <cxxtest/TestSuite.h>
-#define BASE
-#include <input_output/string_utilities.h>
-#undef BASE
 #include "FGJSBBase.h"
+#include <input_output/string_utilities.h>
+
+using namespace JSBSim;
 
 class StringUtilitiesTest : public CxxTest::TestSuite
 {
@@ -95,8 +95,8 @@ class StringUtilitiesTest : public CxxTest::TestSuite
     TS_ASSERT_EQUALS(atof_locale_c("1E-999"), 0.0);
     TS_ASSERT_EQUALS(atof_locale_c("-1E-999"), 0.0);
     TS_ASSERT_EQUALS(atof_locale_c("0.0"), 0.0);
-    TS_ASSERT_THROWS(atof_locale_c("1E+999"), JSBSim::BaseException&);
-    TS_ASSERT_THROWS(atof_locale_c("-1E+999"), JSBSim::BaseException&);
+    TS_ASSERT_THROWS(atof_locale_c("1E+999"), BaseException&);
+    TS_ASSERT_THROWS(atof_locale_c("-1E+999"), BaseException&);
   }
 
 private: