diff --git a/Src/run.c b/Src/run.c
index 925631c..d8162b1 100644
--- a/Src/run.c
+++ b/Src/run.c
@@ -358,7 +358,8 @@ nonprogress(void)	/* np_ */
 
 int
 eval(Lextok *now)
-{
+{	int temp;
+
 	if (now) {
 	lineno = now->ln;
 	Fname  = now->fn;
@@ -373,11 +374,19 @@ eval(Lextok *now)
 	case  UMIN: return -eval(now->lft);
 	case   '~': return ~eval(now->lft);
 
-	case   '/': return (eval(now->lft) / eval(now->rgt));
+	case   '/': temp = eval(now->rgt);
+		    if (temp == 0)
+		    {	fatal("division by zero", (char *) 0);
+		    }
+		    return (eval(now->lft) / temp);
 	case   '*': return (eval(now->lft) * eval(now->rgt));
 	case   '-': return (eval(now->lft) - eval(now->rgt));
 	case   '+': return (eval(now->lft) + eval(now->rgt));
-	case   '%': return (eval(now->lft) % eval(now->rgt));
+	case   '%': temp = eval(now->rgt);
+		    if (temp == 0)
+		    {	fatal("taking modulo of zero", (char *) 0);
+		    }
+		    return (eval(now->lft) % temp);
 	case    LT: return (eval(now->lft) <  eval(now->rgt));
 	case    GT: return (eval(now->lft) >  eval(now->rgt));
 	case   '&': return (eval(now->lft) &  eval(now->rgt));
diff --git a/Src/spin.y b/Src/spin.y
index ec90199..cf72305 100644
--- a/Src/spin.y
+++ b/Src/spin.y
@@ -776,8 +776,18 @@ const_expr:	CONST			{ $$ = $1; }
 	| const_expr '+' const_expr	{ $$ = $1; $$->val = $1->val + $3->val; }
 	| const_expr '-' const_expr	{ $$ = $1; $$->val = $1->val - $3->val; }
 	| const_expr '*' const_expr	{ $$ = $1; $$->val = $1->val * $3->val; }
-	| const_expr '/' const_expr	{ $$ = $1; $$->val = $1->val / $3->val; }
-	| const_expr '%' const_expr	{ $$ = $1; $$->val = $1->val % $3->val; }
+	| const_expr '/' const_expr	{ $$ = $1;
+					  if ($3->val == 0)
+					  { fatal("division by zero", (char *) 0);
+					  }
+					  $$->val = $1->val / $3->val;
+					}
+	| const_expr '%' const_expr	{ $$ = $1;
+					  if ($3->val == 0)
+					  { fatal("attempt to take modulo of zero", (char *) 0);
+					  }
+					  $$->val = $1->val % $3->val;
+					}
 	;
 
 expr    : l_par expr r_par		{ $$ = $2; }
diff --git a/Src/spinlex.c b/Src/spinlex.c
index 35d1fc3..0166546 100644
--- a/Src/spinlex.c
+++ b/Src/spinlex.c
@@ -109,7 +109,9 @@ Getchar(void)
 		return c;	/* expanded select statement */
 	}
 	if (Inlining<0)
-	{	c = getc(yyin);
+	{	do {	c = getc(yyin);
+		} while (c == 0);	// ignore null chars
+		// eventually there will always be an EOF
 	} else
 	{	c = getinline();
 	}
diff --git a/Src/version.h b/Src/version.h
index 8c5b57d..d16230a 100644
--- a/Src/version.h
+++ b/Src/version.h
@@ -6,4 +6,4 @@
  * Tool documentation is available at http://spinroot.com
  */
 
-#define SpinVersion	"Spin Version 6.5.1 -- 29 February 2020"
+#define SpinVersion	"Spin Version 6.5.1 -- 1 March 2020"