diff --git a/libs/gamecode/pr_exec.c b/libs/gamecode/pr_exec.c
index 093ab888c..f5289a3e9 100644
--- a/libs/gamecode/pr_exec.c
+++ b/libs/gamecode/pr_exec.c
@@ -595,6 +595,13 @@ PR_ExecuteProgram (progs_t * pr, func_t fnum)
 				pr->pr_argc = st->op - OP_CALL0;
 				if (!OPA.func_var)
 					PR_RunError (pr, "NULL function");
+				if (OPA.func_var < 0) { // dynamic builtin
+					int i = -OPA.func_var;
+					if (i >= pr->numbuiltins || !pr->builtins[i].proc)
+						PR_RunError (pr, "Bad builtin call number");
+					pr->builtins[i].proc (pr);
+					break;
+				}
 				newf = &pr->pr_functions[OPA.func_var];
 				if (newf->first_statement < 0) {
 					// negative statements are built in functions
diff --git a/qw/source/sv_pr_cmds.c b/qw/source/sv_pr_cmds.c
index 9be53acce..c0b87070a 100644
--- a/qw/source/sv_pr_cmds.c
+++ b/qw/source/sv_pr_cmds.c
@@ -2006,7 +2006,7 @@ PF_checkfunction (progs_t *pr)
 
 	for (i = 0; i < pr->numbuiltins; i++) {
 		if (pr->builtins[i].name && strequal (pr->builtins[i].name, name)) {
-			G_FUNCTION (pr, OFS_RETURN) = i;
+			G_FUNCTION (pr, OFS_RETURN) = -i;
 			return;
 		}
 	}
diff --git a/tools/qfcc/include/qfcc.h b/tools/qfcc/include/qfcc.h
index 07e6ef120..909437c8b 100644
--- a/tools/qfcc/include/qfcc.h
+++ b/tools/qfcc/include/qfcc.h
@@ -549,6 +549,7 @@ typedef struct {
 	int		warn_error;	// treat warnings as errors
 	int		quiet;		// not so much chatter
 	int		debug;		// produce debug info
+	int		undefined_function_warning;	// print a warning when a function isn't defined
 } options_t;
 
 extern options_t options;
diff --git a/tools/qfcc/source/qc-lex.l b/tools/qfcc/source/qc-lex.l
index abfee4e94..36dba6843 100644
--- a/tools/qfcc/source/qc-lex.l
+++ b/tools/qfcc/source/qc-lex.l
@@ -151,6 +151,7 @@ static keyword_t keywords[] = {
 	{"entity",		TYPE,	&type_entity	},
 	{"quaternion",	TYPE,	&type_quaternion},
 	{"integer",		TYPE,	&type_integer	},
+	{"function",	TYPE,	&type_function	},
 	{"local",		LOCAL,	0				},
 	{"return",		RETURN,	0				},
 	{"while",		WHILE,	0				},
diff --git a/tools/qfcc/source/qfcc.c b/tools/qfcc/source/qfcc.c
index 34eff85bc..8fde0afba 100644
--- a/tools/qfcc/source/qfcc.c
+++ b/tools/qfcc/source/qfcc.c
@@ -706,16 +706,16 @@ PR_FinishCompilation (void)
 	expr_t       e;
 
 	// check to make sure all functions prototyped have code
-	for (d = pr.def_head.def_next; d; d = d->def_next) {
-		if (d->type->type == ev_func && !d->scope) {	// function args ok
-//			f = G_FUNCTION(d->ofs);
-//			if (!f || (!f->code && !f->builtin))
-			if (!d->initialized) {
-				printf ("function %s was not defined\n", d->name);
-				errors = true;
+	if (options.undefined_function_warning)
+		for (d = pr.def_head.def_next; d; d = d->def_next) {
+			if (d->type->type == ev_func && !d->scope) {	// function args ok
+//				f = G_FUNCTION(d->ofs);
+//				if (!f || (!f->code && !f->builtin))
+				if (!d->initialized) {
+					warning (0, "function %s was not defined\n", d->name);
+				}
 			}
 		}
-	}
 
 	if (errors)
 		return !errors;
@@ -920,15 +920,16 @@ main (int argc, char **argv)
 	if (CheckParm ("-h") || CheckParm ("--help")) {
 		printf ("%s - A compiler for the QuakeC language\n", argv[0]);
 		printf ("Usage: %s [options]\n", argv[0]);
-		printf ("\
-Options: \n\
-	-s, --source <dir>	look for progs.src in directory <dir>\n\
-	-h, --help		display this help and exit\n\
-	-V, --version		output version information and exit\n\
-	--cow			allow assignment to initialized globals\n\
-	--id			only support id (progs version 6) features\n\
-	--warn=error	treat warnings as errors\n\
-");
+		printf (
+"Options: \n"
+"	-s, --source <dir>	look for progs.src in directory <dir>\n"
+"	-h, --help		display this help and exit\n"
+"	-V, --version		output version information and exit\n"
+"	--cow			allow assignment to initialized globals\n"
+"	--id			only support id (progs version 6) features\n"
+"	--warn=error	treat warnings as errors\n"
+"	--undefined-function-warning	warn when a function isn't defined\n"
+);
 		return 1;
 	}
 
@@ -976,6 +977,10 @@ Options: \n\
 		options.warn_error = 1;
 	}
 
+	if (CheckParm ("--undefined-function-warning")) {
+		options.undefined_function_warning = 1;
+	}
+
 	if (strcmp (sourcedir, ".")) {
 		printf ("Source directory: %s\n", sourcedir);
 	}