diff --git a/esm/Makefile b/esm/Makefile
index 4d7d4098d..9b51817ea 100644
--- a/esm/Makefile
+++ b/esm/Makefile
@@ -1 +1,3 @@
 all: reader
+
+reader: reader.cpp ../tools/stringops.cpp
diff --git a/esm/reader.cpp b/esm/reader.cpp
index e35a8daa6..e75998659 100644
--- a/esm/reader.cpp
+++ b/esm/reader.cpp
@@ -9,6 +9,8 @@ using namespace std;
 #include "../mangle/stream/servers/file_stream.h"
 #include "../mangle/tools/str_exception.h"
 
+#include "../tools/stringops.h"
+
 /* A structure used for holding fixed-length strings. In the case of
    LEN=4, it can be more efficient to match the string as a 32 bit
    number, therefore the struct is implemented as a union with an int.
@@ -87,6 +89,7 @@ class ESMReader
 
   HEDRstruct header;
   SaveData saveData;
+  int spf; // Special file signifier (see SpecialFile below)
 
 public:
   enum Version
@@ -102,6 +105,17 @@ public:
       FT_ESS = 32       // Savegame
     };
 
+  // Used to mark special files. The original ESM files are given
+  // special treatment in a few places, most noticably in loading and
+  // filtering out "dirtly" GMST entries correctly.
+  enum SpecialFile
+    {
+      SF_Other,
+      SF_Morrowind,
+      SF_Tribunal,
+      SF_Bloodmoon
+    };
+
   void open(Mangle::Stream::StreamPtr _esm, const string &name)
   {
     esm = _esm;
@@ -113,7 +127,13 @@ public:
     recName.val = 0;
     subName.val = 0;
 
-    // TODO: determine special file status from file name
+    // Flag certain files for special treatment, based on the file
+    // name.
+    const char *cstr = filename.c_str();
+    if(iends(cstr, "Morrowind.esm")) spf = SF_Morrowind;
+    else if(iends(cstr, "Tribunal.esm")) spf = SF_Tribunal;
+    else if(iends(cstr, "Bloodmoon.esm")) spf = SF_Bloodmoon;
+    else spf = SF_Other;
 
     if(getRecName() != "TES3")
       fail("Not a valid Morrowind file");
diff --git a/tools/stringops.cpp b/tools/stringops.cpp
index a74027179..fcb1aff27 100644
--- a/tools/stringops.cpp
+++ b/tools/stringops.cpp
@@ -1,6 +1,7 @@
 #include "stringops.h"
 
 #include <string.h>
+#include <strings.h>
 
 bool begins(const char* str1, const char* str2)
 {
@@ -23,3 +24,36 @@ bool ends(const char* str1, const char* str2)
 
   return strcmp(str2, str1+len1-len2) == 0;
 }
+
+// True if the given chars match, case insensitive
+static bool icmp(char a, char b)
+{
+  if(a >= 'A' && a <= 'Z')
+    a += 'a' - 'A';
+  if(b >= 'A' && b <= 'Z')
+    b += 'a' - 'A';
+
+  return a == b;
+}
+
+bool ibegins(const char* str1, const char* str2)
+{
+  while(*str2)
+    {
+      if(*str1 == 0 || !icmp(*str1,*str2)) return false;
+
+      str1++;
+      str2++;
+    }
+  return true;
+}
+
+bool iends(const char* str1, const char* str2)
+{
+  int len1 = strlen(str1);
+  int len2 = strlen(str2);
+
+  if(len1 < len2) return false;
+
+  return strcasecmp(str2, str1+len1-len2) == 0;
+}
diff --git a/tools/stringops.h b/tools/stringops.h
index 30c6c1f10..e76b8a87a 100644
--- a/tools/stringops.h
+++ b/tools/stringops.h
@@ -7,4 +7,10 @@ bool begins(const char* str1, const char* str2);
 /// Returns true if str1 ends with substring str2
 bool ends(const char* str1, const char* str2);
 
+/// Case insensitive, returns true if str1 begins with substring str2
+bool ibegins(const char* str1, const char* str2);
+
+/// Case insensitive, returns true if str1 ends with substring str2
+bool iends(const char* str1, const char* str2);
+
 #endif
diff --git a/tools/tests/strops_test.cpp b/tools/tests/strops_test.cpp
index 8991f5623..6c4b3e802 100644
--- a/tools/tests/strops_test.cpp
+++ b/tools/tests/strops_test.cpp
@@ -14,5 +14,35 @@ int main()
   assert(!begins("abc", "bcd"));
   assert(!begins("abc", "abcd"));
 
+  assert(ibegins("Abc", "a"));
+  assert(ibegins("aBc", "ab"));
+  assert(ibegins("abC", "abc"));
+  assert(ibegins("abcD", "abc"));
+
+  assert(!ibegins("abc", "b"));
+  assert(!ibegins("abc", "bc"));
+  assert(!ibegins("abc", "bcd"));
+  assert(!ibegins("abc", "abcd"));
+
+  assert(ends("abc", "c"));
+  assert(ends("abc", "bc"));
+  assert(ends("abc", "abc"));
+  assert(ends("abcd", "abcd"));
+
+  assert(!ends("abc", "b"));
+  assert(!ends("abc", "ab"));
+  assert(!ends("abc", "bcd"));
+  assert(!ends("abc", "abcd"));
+
+  assert(iends("Abc", "c"));
+  assert(iends("aBc", "bc"));
+  assert(iends("abC", "abc"));
+  assert(iends("abcD", "abcd"));
+
+  assert(!iends("abc", "b"));
+  assert(!iends("abc", "ab"));
+  assert(!iends("abc", "bcd"));
+  assert(!iends("abc", "abcd"));
+
   return 0;
 }