diff --git a/c/cvalues.c b/c/cvalues.h
similarity index 99%
rename from c/cvalues.c
rename to c/cvalues.h
index a70ee02..7bfc5ff 100644
--- a/c/cvalues.c
+++ b/c/cvalues.h
@@ -1,4 +1,4 @@
-#include "operators.c"
+#include "operators.h"
 
 #ifdef BITS64
 #define NWORDS(sz) (((sz) + 7) >> 3)
diff --git a/c/equal.c b/c/equal.h
similarity index 100%
rename from c/equal.c
rename to c/equal.h
diff --git a/c/flisp.c b/c/flisp.c
index 585cd49..7a2b37e 100644
--- a/c/flisp.c
+++ b/c/flisp.c
@@ -394,8 +394,8 @@ value_t alloc_vector(size_t n, int init)
 // cvalues
 // --------------------------------------------------------------------
 
-#include "cvalues.c"
-#include "types.c"
+#include "cvalues.h"
+#include "types.h"
 
 // print
 // ----------------------------------------------------------------------
@@ -403,7 +403,7 @@ value_t alloc_vector(size_t n, int init)
 static int isnumtok(char *tok, value_t *pval);
 static inline int symchar(char c);
 
-#include "print.c"
+#include "print.h"
 
 // collector
 // ------------------------------------------------------------------
@@ -747,12 +747,12 @@ int fl_isnumber(value_t v)
 // read
 // -----------------------------------------------------------------------
 
-#include "read.c"
+#include "read.h"
 
 // equal
 // ----------------------------------------------------------------------
 
-#include "equal.c"
+#include "equal.h"
 
 // eval
 // -----------------------------------------------------------------------
diff --git a/c/hashing.c b/c/hashing.c
index c015852..719b93a 100644
--- a/c/hashing.c
+++ b/c/hashing.c
@@ -61,7 +61,7 @@ u_int32_t int64to32hash(u_int64_t key)
     return (u_int32_t)key;
 }
 
-#include "lookup3.c"
+#include "lookup3.h"
 
 u_int64_t memhash(const char *buf, size_t n)
 {
diff --git a/c/lookup3.c b/c/lookup3.h
similarity index 100%
rename from c/lookup3.c
rename to c/lookup3.h
diff --git a/c/mt19937ar.c b/c/mt19937ar.h
similarity index 100%
rename from c/mt19937ar.c
rename to c/mt19937ar.h
diff --git a/c/operators.c b/c/operators.h
similarity index 100%
rename from c/operators.c
rename to c/operators.h
diff --git a/c/print.c b/c/print.h
similarity index 100%
rename from c/print.c
rename to c/print.h
diff --git a/c/random.c b/c/random.c
index 6142700..187d6e8 100644
--- a/c/random.c
+++ b/c/random.c
@@ -10,7 +10,7 @@
 #include "random.h"
 #include "timefuncs.h"
 
-#include "mt19937ar.c"
+#include "mt19937ar.h"
 
 double rand_double()
 {
diff --git a/c/read.c b/c/read.h
similarity index 100%
rename from c/read.c
rename to c/read.h
diff --git a/c/types.c b/c/types.h
similarity index 100%
rename from c/types.c
rename to c/types.h
diff --git a/c/utf8.c b/c/utf8.c
index a4f10bf..ae87353 100644
--- a/c/utf8.c
+++ b/c/utf8.c
@@ -256,7 +256,7 @@ size_t u8_strlen(const char *s)
 }
 
 #if defined(__WIN32__)
-#include "wcwidth.c"
+#include "wcwidth.h"
 #endif
 
 size_t u8_strwidth(const char *s)
diff --git a/c/wcwidth.c b/c/wcwidth.h
similarity index 100%
rename from c/wcwidth.c
rename to c/wcwidth.h