diff --git a/usr.bin/yacc/defs.h b/usr.bin/yacc/defs.h
index 4efc8a39610c..cb8b083bff41 100644
--- a/usr.bin/yacc/defs.h
+++ b/usr.bin/yacc/defs.h
@@ -47,9 +47,6 @@
 /*  the following definitions are for the Tahoe		*/
 /*  they might have to be changed for other machines	*/
 
-/*  MAXCHAR is the largest unsigned character value	*/
-/*  MAXSHORT is the largest value of a C short		*/
-/*  MINSHORT is the most negative value of a C short	*/
 /*  MAXTABLE is the maximum table size			*/
 /*  BITS_PER_WORD is the number of bits in a C unsigned	*/
 /*  WORDSIZE computes the number of words needed to	*/
@@ -58,9 +55,6 @@
 /*	from r (0-indexed)				*/
 /*  SETBIT sets the n-th bit starting from r		*/
 
-#define	MAXCHAR		255
-#define	MAXSHORT	32767
-#define MINSHORT	-32768
 #define MAXTABLE	32500
 #define BITS_PER_WORD	32
 #define	WORDSIZE(n)	(((n)+(BITS_PER_WORD-1))/BITS_PER_WORD)
diff --git a/usr.bin/yacc/lalr.c b/usr.bin/yacc/lalr.c
index 3fe94fbbd6bd..95d87de2dc1e 100644
--- a/usr.bin/yacc/lalr.c
+++ b/usr.bin/yacc/lalr.c
@@ -43,6 +43,7 @@ static char sccsid[] = "@(#)lalr.c	5.3 (Berkeley) 6/1/90";
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <limits.h>
 #include <stdlib.h>
 #include "defs.h"
 
@@ -252,7 +253,7 @@ set_goto_map()
 
 	  if (ISTOKEN(symbol)) break;
 
-	  if (ngotos == MAXSHORT)
+	  if (ngotos == SHRT_MAX)
 	    fatal("too many gotos");
 
 	  ngotos++;
diff --git a/usr.bin/yacc/lr0.c b/usr.bin/yacc/lr0.c
index efeaed236f27..cd8d1a1e624e 100644
--- a/usr.bin/yacc/lr0.c
+++ b/usr.bin/yacc/lr0.c
@@ -43,6 +43,7 @@ static char sccsid[] = "@(#)lr0.c	5.3 (Berkeley) 1/20/91";
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <limits.h>
 #include <stdlib.h>
 #include "defs.h"
 
@@ -358,7 +359,7 @@ int symbol;
     fprintf(stderr, "Entering new_state(%d)\n", symbol);
 #endif
 
-    if (nstates >= MAXSHORT)
+    if (nstates >= SHRT_MAX)
 	fatal("too many states");
 
     isp1 = kernel_base[symbol];
diff --git a/usr.bin/yacc/output.c b/usr.bin/yacc/output.c
index 835f21e7fad4..b0b520a7e30d 100644
--- a/usr.bin/yacc/output.c
+++ b/usr.bin/yacc/output.c
@@ -43,6 +43,7 @@ static char sccsid[] = "@(#)output.c	5.7 (Berkeley) 5/24/93";
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <limits.h>
 #include <stdlib.h>
 #include <string.h>
 #include "defs.h"
@@ -331,7 +332,7 @@ token_actions()
 	    {
 		froms[i] = r = NEW2(shiftcount, short);
 		tos[i] = s = NEW2(shiftcount, short);
-		min = MAXSHORT;
+		min = SHRT_MAX;
 		max = 0;
 		for (j = 0; j < ntokens; ++j)
 		{
@@ -351,7 +352,7 @@ token_actions()
 	    {
 		froms[nstates+i] = r = NEW2(reducecount, short);
 		tos[nstates+i] = s = NEW2(reducecount, short);
-		min = MAXSHORT;
+		min = SHRT_MAX;
 		max = 0;
 		for (j = 0; j < ntokens; ++j)
 		{
diff --git a/usr.bin/yacc/reader.c b/usr.bin/yacc/reader.c
index 5beb19990b19..3e01e8f0c91a 100644
--- a/usr.bin/yacc/reader.c
+++ b/usr.bin/yacc/reader.c
@@ -43,6 +43,7 @@ static char sccsid[] = "@(#)reader.c	5.7 (Berkeley) 1/20/91";
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <limits.h>
 #include <stdlib.h>
 #include <string.h>
 #include "defs.h"
@@ -720,7 +721,7 @@ get_literal()
 			++cptr;
 		    }
 		}
-		if (n > MAXCHAR) illegal_character(c_cptr);
+		if (n > UCHAR_MAX) illegal_character(c_cptr);
 		c = n;
 	    	break;
 
@@ -736,7 +737,7 @@ get_literal()
 		    if (i < 0 || i >= 16) break;
 		    ++cptr;
 		    n = (n << 4) + i;
-		    if (n > MAXCHAR) illegal_character(c_cptr);
+		    if (n > UCHAR_MAX) illegal_character(c_cptr);
 		}
 		c = n;
 		break;