diff --git a/compiler/parser/Parser.y.pp b/compiler/parser/Parser.y.pp
index 34c0bc6901d8..483ed87591ab 100644
--- a/compiler/parser/Parser.y.pp
+++ b/compiler/parser/Parser.y.pp
@@ -26,8 +26,16 @@
 
 -- CPP tricks because we want the directives in the output of the
 -- first CPP pass.
+--
+-- Clang note, 6/17/2013 by aseipp: It is *extremely* important (for
+-- some reason) that there be a line of whitespace between the two
+-- definitions here, and the subsequent use of __IF_GHC_77__ - this
+-- seems to be a bug in clang or something, where having the line of
+-- whitespace will make the preprocessor correctly format the rendered
+-- lines in the 'two step' CPP pass. No, this is not a joke.
 #define __IF_GHC_77__ #if __GLASGOW_HASKELL__ >= 707
-#define __ENDIF__     #endif
+#define __ENDIF__ #endif
+
 __IF_GHC_77__
 -- Required on x86 to avoid the register allocator running out of
 -- stack slots when compiling this module with -fPIC -dynamic.