diff --git a/usr.bin/m4/eval.c b/usr.bin/m4/eval.c
index 9e5162f26993..c857b91c63f3 100644
--- a/usr.bin/m4/eval.c
+++ b/usr.bin/m4/eval.c
@@ -269,8 +269,12 @@ expand_builtin(const char *argv[], int argc, int td)
 	case INCLTYPE:
 		if (argc > 2)
 			if (!doincl(argv[2]))
-				err(1, "%s at line %lu: include(%s)",
-				    CURRENT_NAME, CURRENT_LINE, argv[2]);
+				if (mimic_gnu) 
+					warn("%s at line %lu: include(%s)",
+					    CURRENT_NAME, CURRENT_LINE, argv[2]);
+				else
+					err(1, "%s at line %lu: include(%s)",
+					    CURRENT_NAME, CURRENT_LINE, argv[2]);
 		break;
 
 	case SINCTYPE:
diff --git a/usr.bin/m4/parser.y b/usr.bin/m4/parser.y
index fac670931337..deda9625547e 100644
--- a/usr.bin/m4/parser.y
+++ b/usr.bin/m4/parser.y
@@ -18,6 +18,7 @@
  * $FreeBSD$
  */
 #include <stdint.h>
+#include <math.h>
 #define YYSTYPE	int32_t
 extern int32_t end_result;
 extern int yylex(void);
@@ -34,6 +35,7 @@ extern int yyparse(void);
 %left EQ NE
 %left '<' LE '>' GE
 %left LSHIFT RSHIFT
+%right EXPONENT
 %left '+' '-'
 %left '*' '/' '%'
 %right UMINUS UPLUS '!' '~'
@@ -44,6 +46,7 @@ top	: expr { end_result = $1; }
 	;
 expr 	: expr '+' expr { $$ = $1 + $3; }
      	| expr '-' expr { $$ = $1 - $3; }
+	| expr EXPONENT expr { $$ = pow($1, $3); }
      	| expr '*' expr { $$ = $1 * $3; }
 	| expr '/' expr {
 		if ($3 == 0) {
diff --git a/usr.bin/m4/tokenizer.l b/usr.bin/m4/tokenizer.l
index e9c9e129aec8..ca3612e41441 100644
--- a/usr.bin/m4/tokenizer.l
+++ b/usr.bin/m4/tokenizer.l
@@ -57,6 +57,7 @@ radix	0[rR][0-9]+:[0-9a-zA-Z]+
 "!="			{ return(NE); }
 "&&"			{ return(LAND); }
 "||"			{ return(LOR); }
+"**"			{ if (mimic_gnu) { return (EXPONENT); } }
 .			{ return yytext[0]; }
 %%