diff --git a/preprocessor.cpp b/preprocessor.cpp
index 5440f11f3..8f791f87a 100644
--- a/preprocessor.cpp
+++ b/preprocessor.cpp
@@ -1,4 +1,4 @@
-/*
+/*
  * c++check - c/c++ syntax checking
  * Copyright (C) 2007 Daniel Marjamäki
  *
@@ -125,6 +125,42 @@ void preprocess(std::istream &istr, std::map<std::string, std::string> &result)
 
 
 
+// Get the DEF in this line: "#ifdef DEF"
+static std::string getdef(std::string line, bool def)
+{
+    // Replace tabs with spaces..
+    while ( line.find("\t") != std::string::npos )
+        line[ line.find("\t") ] = 0;
+
+    // Trim off any leading spaces..
+    while (line[0] == ' ')
+        line.erase(0, 1);
+
+    // If def is true, the line must start with "#ifdef"
+    if ( def && line.find("#ifdef ") != 0 )
+    {
+        return "";
+    }
+
+    // If def is false, the line must start with "#ifndef"
+    if ( !def && line.find("#ifndef ") != 0 )
+    {
+        return "";
+    }
+
+    // Remove the "#ifdef" or "#ifndef"
+    line.erase( 0, line.find(" ") );
+
+    // Remove all spaces.
+    while ( line.find(" ") != std::string::npos )
+        line.erase( line.find(" "), 1 );
+
+    // The remaining string is our result.
+    return line;
+}
+
+
+
 static std::list<std::string> getcfgs( const std::string &filedata )
 {
     std::list<std::string> ret;
@@ -134,9 +170,9 @@ static std::list<std::string> getcfgs( const std::string &filedata )
     std::string line;
     while ( getline(istr, line) )
     {
-        if ( line.find("#ifdef ")==0 || line.find("#ifndef ")==0 )
+        std::string def = getdef(line, true) + getdef(line, false);
+        if (!def.empty())
         {
-            std::string def( line.substr(line.find(" ") + 1) );
             if (std::find(ret.begin(), ret.end(), def) == ret.end())
                 ret.push_back( def );
         }
@@ -158,11 +194,14 @@ static std::string getcode(const std::string &filedata, std::string cfg)
     std::string line;
     while ( getline(istr, line) )
     {
-        if ( line.find("#ifdef ") == 0 )
-            matching_ifdef.push_back( !cfg.empty() && line.find(cfg) != std::string::npos );
+        std::string def = getdef( line, true );
+        std::string ndef = getdef( line, false );
 
-        else if ( line.find("#ifndef ") == 0 )
-            matching_ifdef.push_back( cfg.empty() || line.find(cfg) == std::string::npos );
+        if ( ! def.empty() )
+            matching_ifdef.push_back( cfg == def );
+
+        else if ( ! ndef.empty() )
+            matching_ifdef.push_back( cfg != ndef );
 
         else if ( line.find("#else") == 0)
             matching_ifdef.back() = ! matching_ifdef.back();
diff --git a/preprocessor.h b/preprocessor.h
index a349aba64..89810b132 100644
--- a/preprocessor.h
+++ b/preprocessor.h
@@ -1,4 +1,4 @@
-/*
+/*
  * c++check - c/c++ syntax checking
  * Copyright (C) 2007 Daniel Marjamäki
  *
diff --git a/testpreprocessor.cpp b/testpreprocessor.cpp
index 40d1a0916..92ac58f15 100644
--- a/testpreprocessor.cpp
+++ b/testpreprocessor.cpp
@@ -1,111 +1,113 @@
-/*
- * c++check - c/c++ syntax checking
- * Copyright (C) 2007 Daniel Marjamäki
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/
- */
-
-
-// The preprocessor that c++check uses is a bit special. Instead of generating
-// the code for a known configuration, it generates the code for each configuration.
-
-
-#include "testsuite.h"
-#include "preprocessor.h"
-
-#include <map>
-#include <string>
-
-class TestPreprocessor : public TestFixture
-{
-public:
-    TestPreprocessor() : TestFixture("TestPreprocessor")
-    { }
-
-private:
-
-    void run()
-    {
-        TEST_CASE( test1 );
-        TEST_CASE( test2 );
-
-        TEST_CASE( comments1 );
-    }
-
-    void check(const char filedata[], const std::map<std::string,std::string> &expected)
-    {
-        std::istringstream istr(filedata);
-        std::map<std::string, std::string> actual;
-        preprocess( istr, actual );
-
-        ASSERT_EQUALS( expected.size(), actual.size() );
-        for ( std::map<std::string,std::string>::const_iterator it = actual.begin(); it != actual.end(); ++it )
-        {
-            std::map<std::string,std::string>::const_iterator it2 = expected.find(it->first);
-            if ( it2 == expected.end() )
-                assertFail(__FILE__, __LINE__);
-            else
-            {
-                std::string s1 = it->second;
-                std::string s2 = it2->second;
-                ASSERT_EQUALS( it->second, it2->second );
-            }
-        }
-    }
-
-    void test1()
-    {
-        const char filedata[] = "#ifdef WIN32\n"
-                                "    abcdef\n"
-                                "#else\n"
-                                "    qwerty\n"
-                                "#endif\n";
-
-        std::map<std::string, std::string> expected;
-        expected[""]      = "\n\n\n    qwerty\n\n";
-        expected["WIN32"] = "\n    abcdef\n\n\n\n";
-
-        check( filedata, expected );
-    }
-
-    void test2()
-    {
-        const char filedata[] = "#ifndef WIN32\n"
-                                "    abcdef\n"
-                                "#else\n"
-                                "    qwerty\n"
-                                "#endif\n";
-
-        std::map<std::string, std::string> expected;
-        expected[""]      = "\n    abcdef\n\n\n\n";
-        expected["WIN32"] = "\n\n\n    qwerty\n\n";
-
-        check( filedata, expected );
-    }
-
-    void comments1()
-    {
-        const char filedata[] = "/*\n"
-                                "#ifdef WIN32\n"
-                                "#endif\n"
-                                "*/\n";
-
-        std::map<std::string, std::string> expected;
-        expected[""] = "\n\n\n\n";
-        check( filedata, expected );
-    }
-
-};
-
-REGISTER_TEST( TestPreprocessor )
+/*
+ * c++check - c/c++ syntax checking
+ * Copyright (C) 2007 Daniel Marjamäki
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/
+ */
+
+
+// The preprocessor that c++check uses is a bit special. Instead of generating
+// the code for a known configuration, it generates the code for each configuration.
+
+
+#include "testsuite.h"
+#include "preprocessor.h"
+
+#include <map>
+#include <string>
+
+class TestPreprocessor : public TestFixture
+{
+public:
+    TestPreprocessor() : TestFixture("TestPreprocessor")
+    { }
+
+private:
+
+    void run()
+    {
+        TEST_CASE( test1 );
+        TEST_CASE( test2 );
+
+        TEST_CASE( comments1 );
+    }
+
+    void check(const char filedata[], const std::map<std::string,std::string> &expected)
+    {
+        std::istringstream istr(filedata);
+        std::map<std::string, std::string> actual;
+        preprocess( istr, actual );
+
+        ASSERT_EQUALS( expected.size(), actual.size() );
+        for ( std::map<std::string,std::string>::const_iterator it = actual.begin(); it != actual.end(); ++it )
+        {
+            std::map<std::string,std::string>::const_iterator it2 = expected.find(it->first);
+            if ( it2 == expected.end() )
+                assertFail(__FILE__, __LINE__);
+            else
+            {
+                std::string s1 = it->second;
+                std::string s2 = it2->second;
+                ASSERT_EQUALS( it->second, it2->second );
+            }
+        }
+    }
+
+    void test1()
+    {
+        const char filedata[] = "#ifdef  WIN32 \n"
+                                "    abcdef\n"
+                                "#else\n"
+                                "    qwerty\n"
+                                "#endif\n";
+
+        std::map<std::string, std::string> expected;
+        expected[""]      = "\n\n\n    qwerty\n\n";
+        expected["WIN32"] = "\n    abcdef\n\n\n\n";
+
+        check( filedata, expected );
+    }
+
+    void test2()
+    {
+        const char filedata[] = "#ifndef WIN32\n"
+                                "    abcdef\n"
+                                "#else\n"
+                                "    qwerty\n"
+                                "#endif\n";
+
+        std::map<std::string, std::string> expected;
+        expected[""]      = "\n    abcdef\n\n\n\n";
+        expected["WIN32"] = "\n\n\n    qwerty\n\n";
+
+        check( filedata, expected );
+    }
+
+
+
+    void comments1()
+    {
+        const char filedata[] = "/*\n"
+                                "#ifdef WIN32\n"
+                                "#endif\n"
+                                "*/\n";
+
+        std::map<std::string, std::string> expected;
+        expected[""] = "\n\n\n\n";
+        check( filedata, expected );
+    }
+
+};
+
+REGISTER_TEST( TestPreprocessor )