diff -up chemtool-1.6.14/ct1.h.gcc10 chemtool-1.6.14/ct1.h
--- chemtool-1.6.14/ct1.h.gcc10	2011-12-23 20:30:53.000000000 +0100
+++ chemtool-1.6.14/ct1.h	2020-02-20 12:04:09.081966039 +0100
@@ -273,12 +273,12 @@ extern int nbonds;
 extern float importfactor;
 extern int importoffset;
 
-char **intype;
-char **inmode;
-int babelin;
-char **outtype;
-char **outmode;
-int babelout;
+extern char **intype;
+extern char **inmode;
+extern int babelin;
+extern char **outtype;
+extern char **outmode;
+extern int babelout;
 extern char *babel;
 extern GdkGC *mygc[8],*background_gc,*hlgc;
 extern int curpen;
diff -up chemtool-1.6.14/inout.c.gcc10 chemtool-1.6.14/inout.c
--- chemtool-1.6.14/inout.c.gcc10	2013-08-13 01:39:43.000000000 +0200
+++ chemtool-1.6.14/inout.c	2020-02-20 12:10:29.141059205 +0100
@@ -31,6 +31,12 @@ extern GdkFont *font[7],*smallfont[7],*s
 #endif
 
 static char babeloutp[4];
+int babelin;
+int babelout;
+char **inmode;
+char **intype;
+char **outmode;
+char **outtype;
 
 int
 save_mol (FILE * fp, int partial)