diff --git a/buddy/examples/bddtest/bddtest.cxx b/buddy/examples/bddtest/bddtest.cxx
index 3e1444e24..3478a65bc 100644
--- a/buddy/examples/bddtest/bddtest.cxx
+++ b/buddy/examples/bddtest/bddtest.cxx
@@ -8,7 +8,7 @@ static const int varnum = 5;
   Example of allsat print handler.
 **************************************************************************/
 
-void allsatHandlerPrint(char* varset, int size)
+void allsatHandlerPrint(signed char* varset, int size)
 {
   using namespace std ;
   for (int v=0; v<size ; ++v)
@@ -26,7 +26,7 @@ void allsatHandlerPrint(char* varset, int size)
 static bdd allsatBDD;
 static bdd allsatSumBDD;
 
-void allsatHandler(char* varset, int size)
+void allsatHandler(signed char* varset, int size)
 {
   bdd x = bddtrue;
   for (int v=0 ; v<size ; ++v)
diff --git a/buddy/src/bddop.c b/buddy/src/bddop.c
index 5592ee232..7adaea55b 100644
--- a/buddy/src/bddop.c
+++ b/buddy/src/bddop.c
@@ -122,7 +122,7 @@ static int firstReorder;            /* Used instead of local variable in order
 				       to avoid compiler warning about 'first'
 				       being clobbered by setjmp */
 
-static char*            allsatProfile; /* Variable profile for bdd_allsat() */
+static signed char*     allsatProfile; /* Variable profile for bdd_allsat() */
 static bddallsathandler allsatHandler; /* Callback handler for bdd_allsat() */
 
 extern bddCacheStat bddcachestats;
@@ -2691,7 +2691,7 @@ DESCR   {* Iterates through all legal variable assignments (those
 	   The following is an example of a callback handler that
 	   prints 'X' for don't cares, '0' for zero, and '1' for one:
 	   \begin{verbatim}
-void allsatPrintHandler(char* varset, int size)
+void allsatPrintHandler(signed char* varset, int size)
 {
   for (int v=0; v<size ; ++v)
   {
@@ -2713,7 +2713,7 @@ void bdd_allsat(BDD r, bddallsathandler handler)
 
    CHECKn(r);
 
-   if (__unlikely((allsatProfile=(char*)malloc(bddvarnum)) == NULL))
+   if (__unlikely((allsatProfile=(signed char*)malloc(bddvarnum)) == NULL))
    {
       bdd_error(BDD_MEMORY);
       return;
diff --git a/buddy/src/bddx.h b/buddy/src/bddx.h
index 957385b4f..573569c7f 100644
--- a/buddy/src/bddx.h
+++ b/buddy/src/bddx.h
@@ -268,7 +268,7 @@ typedef void (*bddgbchandler)(int,bddGbcStat*);
 typedef void (*bdd2inthandler)(int,int);
 typedef int  (*bddsizehandler)(void);
 typedef void (*bddfilehandler)(FILE *, int);
-typedef void (*bddallsathandler)(char*, int);
+typedef void (*bddallsathandler)(signed char*, int);
 
 BUDDY_API bddinthandler  bdd_error_hook(bddinthandler);
 BUDDY_API bddgbchandler  bdd_gbc_hook(bddgbchandler);