diff --git a/Main.hs b/Main.hs
index ca5c396..992e40f 100644
--- a/Main.hs
+++ b/Main.hs
@@ -244,7 +244,7 @@ compileFull inputFile moutputFile
                           -- using a stem (input file minus known extension).
                           -- If the extension isn't known, the user must specify
                           -- the output file
-                          ("-", Just file) -> return file
+                          ("-", Just file) -> return $ file ++ ".tock"
                           ("-", Nothing) -> dieReport (Nothing, "Must specify an output file when using full-compile mode")
                           (file, _) -> return file
 
@@ -287,7 +287,7 @@ compileFull inputFile moutputFile
                  exec $ cCommand postCFile postOFile (csCompilerFlags optsPS)
 
                  cs <- lift getCompState
-                 let otherOFiles = [usedFile ++ ".o"
+                 let otherOFiles = [usedFile ++ ".tock.o"
                                    | usedFile <- Set.toList $ csUsedFiles cs]
                    
 
diff --git a/backends/GenerateC.hs b/backends/GenerateC.hs
index 591192b..1209c94 100644
--- a/backends/GenerateC.hs
+++ b/backends/GenerateC.hs
@@ -170,7 +170,7 @@ cgenTopLevel headerName s
 
           tell ["#include \"", dropPath headerName, "\"\n"]
 
-          sequence_ [tell ["#include \"", usedFile, ".h\"\n"]
+          sequence_ [tell ["#include \"", usedFile, ".tock.h\"\n"]
                     | usedFile <- Set.toList $ csUsedFiles cs]
 
           sequence_ [tell ["extern int "] >> genName n >> tell ["_stack_size;\n"]
diff --git a/cgtests.mk b/cgtests.mk
index f09b5a7..1b7cf99 100644
--- a/cgtests.mk
+++ b/cgtests.mk
@@ -6,15 +6,15 @@ tests = $(patsubst %.occ,%,$(wildcard cgtests/cgtest??.occ))
 all: $(tests)
 
 clean:
-	rm -f $(tests) cgtests/cglib.inc
+	rm -f $(tests) cgtests/cglib.tock.inc
 
 checkout:
 	svn co http://projects.cs.kent.ac.uk/projects/kroc/svn/kroc/trunk/tests/cgtests
 
-%: %.occ cgtests/cglib.inc
-	./tock -vk --backend=$(BACKEND) --usage-checking=off --run-indent -o $@ $<
+%: %.occ cgtests/cglib.tock.inc
+	./tock -vk --backend=$(BACKEND) --usage-checking=off --run-indent $<
 
-cgtests/cglib.inc: cgtests/cglib.occ
+cgtests/cglib.tock.inc: cgtests/cglib.occ
 	./tock -vk --backend=$(BACKEND) --usage-checking=off --run-indent --no-main $<
 
 run: $(tests)
diff --git a/frontends/PreprocessOccam.hs b/frontends/PreprocessOccam.hs
index 4ab4d01..d1e6d12 100644
--- a/frontends/PreprocessOccam.hs
+++ b/frontends/PreprocessOccam.hs
@@ -65,9 +65,9 @@ preprocessFile m filename
     =  do (handle, realFilename) <- searchFile m filename
           progress $ "Loading source file " ++ realFilename
           origCS <- get
-          let modFunc = if drop4 filename `Set.member` csUsedFiles origCS
-                          then Set.insert (drop4 realFilename)
-                                 . Set.delete (drop4 filename)
+          let modFunc = if drop9 filename `Set.member` csUsedFiles origCS
+                          then Set.insert (drop9 realFilename)
+                                 . Set.delete (drop9 filename)
                           else id
           modify (\cs -> cs { csCurrentFile = realFilename
                             , csUsedFiles = modFunc $ csUsedFiles cs })
@@ -76,8 +76,8 @@ preprocessFile m filename
           modify (\cs -> cs { csCurrentFile = csCurrentFile origCS })
           return toks
   where
-    -- drops 4 from the end:
-    drop4 = reverse . drop 4 . reverse
+    -- drops 9 (i.e. length ".tock.inc") from the end:
+    drop9 = reverse . drop 9 . reverse
 
 -- | Preprocesses source directly and returns its tokenised form ready for parsing.
 preprocessSource :: Meta -> String -> String -> PassM [Token]
@@ -199,7 +199,7 @@ handleUse m [modName]
           put $ cs { csUsedFiles = Set.insert incName (csUsedFiles cs) }
           if Set.member incName (csUsedFiles cs)
             then return return
-            else handleInclude m [incName ++ ".inc"]
+            else handleInclude m [incName ++ ".tock.inc"]
   where
     -- | If a module name has a suffix, strip it
     mangleModName :: String -> String