diff --git a/mozilla/js/js2/parser.cpp b/mozilla/js/js2/parser.cpp
index 5dd3beda467..41146fcb605 100644
--- a/mozilla/js/js2/parser.cpp
+++ b/mozilla/js/js2/parser.cpp
@@ -39,6 +39,7 @@ JS::Reader::Reader(const String &source, const String &sourceLocation, uint32 in
 	begin = b;
 	p = b;
 	end = b + Reader::source.size();
+	Reader::source.append(uni::null);   // ensure last character is always '\0'
   #ifdef DEBUG
 	recordString = 0;
   #endif
diff --git a/mozilla/js/js2/parser.h b/mozilla/js/js2/parser.h
index 3156002aef1..74b93bde1d4 100644
--- a/mozilla/js/js2/parser.h
+++ b/mozilla/js/js2/parser.h
@@ -40,7 +40,7 @@ namespace JavaScript {
 		const char16 *p;				// Position in source text
 		const char16 *end;				// End of source text; *end is a null character
 	  public:
-		const String source;			// Source text
+		String source;			        // Source text
 		const String sourceLocation;	// Description of location from which the source text came
 	  private:
 		const uint32 initialLineNum;	// One-based number of current line
diff --git a/mozilla/js2/src/parser.cpp b/mozilla/js2/src/parser.cpp
index 5dd3beda467..41146fcb605 100644
--- a/mozilla/js2/src/parser.cpp
+++ b/mozilla/js2/src/parser.cpp
@@ -39,6 +39,7 @@ JS::Reader::Reader(const String &source, const String &sourceLocation, uint32 in
 	begin = b;
 	p = b;
 	end = b + Reader::source.size();
+	Reader::source.append(uni::null);   // ensure last character is always '\0'
   #ifdef DEBUG
 	recordString = 0;
   #endif
diff --git a/mozilla/js2/src/parser.h b/mozilla/js2/src/parser.h
index 3156002aef1..74b93bde1d4 100644
--- a/mozilla/js2/src/parser.h
+++ b/mozilla/js2/src/parser.h
@@ -40,7 +40,7 @@ namespace JavaScript {
 		const char16 *p;				// Position in source text
 		const char16 *end;				// End of source text; *end is a null character
 	  public:
-		const String source;			// Source text
+		String source;			        // Source text
 		const String sourceLocation;	// Description of location from which the source text came
 	  private:
 		const uint32 initialLineNum;	// One-based number of current line