--- a/src/cosmo.c
+++ b/src/cosmo.c
@@ -39,6 +39,11 @@
 #include "cosmo.h"
 #include "lf.h"
 
+char    gstr[MAXCHAR];
+int   bswapflag;
+
+double  H, H0, OmegaM, OmegaL, deltaMH;
+
 /******************************** cosmo_dconf ********************************/
 /*
 Conformal distance. Numerical integration along geodesic, allowing for a
--- a/src/cosmo.h
+++ b/src/cosmo.h
@@ -38,7 +38,7 @@
 
 /*------------------------------ global variables ---------------------------*/
 
-double	H, H0, OmegaM, OmegaL, deltaMH;
+extern double	H, H0, OmegaM, OmegaL, deltaMH;
 
 /*-------------------------------- protos -----------------------------------*/
 
--- a/src/globals.h
+++ b/src/globals.h
@@ -29,8 +29,8 @@
 #include	"types.h"
 
 /*----------------------- miscellaneous variables ---------------------------*/
-char		gstr[MAXCHAR];
-int		bswapflag;
+extern char		gstr[MAXCHAR];
+extern int		bswapflag;
 
 /*------------------------------- functions ---------------------------------*/
 extern	void	error(int, char *, char *),
--- a/src/prefs.c
+++ b/src/prefs.c
@@ -53,6 +53,8 @@
 #include 	"prefs.h"
 #include	"preflist.h"
 
+prefstruct  prefs;
+
 /********************************* dumpprefs ********************************/
 /*
 Print the default preference parameters.
--- a/src/prefs.h
+++ b/src/prefs.h
@@ -136,7 +136,7 @@
   double	time_diff;			/* Execution time */
   }	prefstruct;
 
-prefstruct	prefs;
+extern prefstruct	prefs;
 
 /*----------------------------- Internal constants --------------------------*/