diff -r 16776952390a sys/src/cmd/1c/cgen.c
--- a/sys/src/cmd/1c/cgen.c	Tue Jun 18 13:29:29 2019 +0200
+++ b/sys/src/cmd/1c/cgen.c	Wed Jun 19 14:09:29 2019 +0200
@@ -376,10 +376,7 @@
 
 	case OCAST:
 		if(result == D_NONE) {
-			if(n->type != types[TVOID])
-				nullwarn(l, Z);
-			else
-				cgen(l, D_NONE, Z);
+			cgen(l, D_NONE, Z);
 			break;
 		}
 		lg = result;
diff -r 16776952390a sys/src/cmd/2c/cgen.c
--- a/sys/src/cmd/2c/cgen.c	Tue Jun 18 13:29:29 2019 +0200
+++ b/sys/src/cmd/2c/cgen.c	Wed Jun 19 14:09:29 2019 +0200
@@ -376,10 +376,7 @@
 
 	case OCAST:
 		if(result == D_NONE) {
-			if(n->type != types[TVOID])
-				nullwarn(l, Z);
-			else
-				cgen(l, D_NONE, Z);
+			cgen(l, D_NONE, Z);
 			break;
 		}
 		lg = result;
diff -r 16776952390a sys/src/cmd/5c/cgen.c
--- a/sys/src/cmd/5c/cgen.c	Tue Jun 18 13:29:29 2019 +0200
+++ b/sys/src/cmd/5c/cgen.c	Wed Jun 19 14:09:29 2019 +0200
@@ -399,10 +399,7 @@
 
 	case OCAST:
 		if(nn == Z) {
-			if(n->type != types[TVOID])
-				nullwarn(l, Z);
-			else
-				cgen(l, Z);
+			cgen(l, Z);
 			break;
 		}
 		/*
@@ -927,7 +924,7 @@
 
 	case OCAST:
 		if(nn == Z){
-			nullwarn(l, Z);
+			cgen(l, Z);
 			goto Out;
 		}
 		if(typeilp[n->type->etype] && typev[l->type->etype]){
diff -r 16776952390a sys/src/cmd/6c/cgen.c
--- a/sys/src/cmd/6c/cgen.c	Tue Jun 18 13:29:29 2019 +0200
+++ b/sys/src/cmd/6c/cgen.c	Wed Jun 19 14:09:29 2019 +0200
@@ -976,10 +976,7 @@
 
 	case OCAST:
 		if(nn == Z) {
-			if(n->type != types[TVOID])
-				nullwarn(l, Z);
-			else
-				cgen(l, Z);
+			cgen(l, Z);
 			break;
 		}
 		/*
diff -r 16776952390a sys/src/cmd/7c/cgen.c
--- a/sys/src/cmd/7c/cgen.c	Tue Jun 18 13:29:29 2019 +0200
+++ b/sys/src/cmd/7c/cgen.c	Wed Jun 19 14:09:29 2019 +0200
@@ -442,7 +442,7 @@
 
 	case OCAST:
 		if(nn == Z) {
-			nullwarn(l, Z);
+			cgen(l, Z);
 			break;
 		}
 		/*
diff -r 16776952390a sys/src/cmd/8c/cgen.c
--- a/sys/src/cmd/8c/cgen.c	Tue Jun 18 13:29:29 2019 +0200
+++ b/sys/src/cmd/8c/cgen.c	Wed Jun 19 14:09:29 2019 +0200
@@ -994,10 +994,7 @@
 
 	case OCAST:
 		if(nn == Z) {
-			if(n->type != types[TVOID])
-				nullwarn(l, Z);
-			else
-				cgen(l, Z);
+			cgen(l, Z);
 			break;
 		}
 		/*
diff -r 16776952390a sys/src/cmd/cc/com.c
--- a/sys/src/cmd/cc/com.c	Tue Jun 18 13:29:29 2019 +0200
+++ b/sys/src/cmd/cc/com.c	Wed Jun 19 14:09:29 2019 +0200
@@ -1054,6 +1054,11 @@
 
 	case OCAST:
 		ccom(l);
+		if(n->type == types[TVOID] && !side(l)){
+			n->left = Z;
+			n->type = T;
+			break;
+		}
 		if(l->op == OCONST) {
 			evconst(n);
 			if(n->op == OCONST)
diff -r 16776952390a sys/src/cmd/kc/cgen.c
--- a/sys/src/cmd/kc/cgen.c	Tue Jun 18 13:29:29 2019 +0200
+++ b/sys/src/cmd/kc/cgen.c	Wed Jun 19 14:09:29 2019 +0200
@@ -358,10 +358,7 @@
 
 	case OCAST:
 		if(nn == Z) {
-			if(n->type != types[TVOID])
-				nullwarn(l, Z);
-			else
-				cgen(l, Z);
+			cgen(l, Z);
 			break;
 		}
 		/*
diff -r 16776952390a sys/src/cmd/qc/cgen.c
--- a/sys/src/cmd/qc/cgen.c	Tue Jun 18 13:29:29 2019 +0200
+++ b/sys/src/cmd/qc/cgen.c	Wed Jun 19 14:09:29 2019 +0200
@@ -395,10 +395,7 @@
 
 	case OCAST:
 		if(nn == Z) {
-			if(n->type != types[TVOID])
-				nullwarn(l, Z);
-			else
-				cgen(l, Z);
+			cgen(l, Z);
 			break;
 		}
 		/*
diff -r 16776952390a sys/src/cmd/vc/cgen.c
--- a/sys/src/cmd/vc/cgen.c	Tue Jun 18 13:29:29 2019 +0200
+++ b/sys/src/cmd/vc/cgen.c	Wed Jun 19 14:09:29 2019 +0200
@@ -359,10 +359,7 @@
 
 	case OCAST:
 		if(nn == Z) {
-			if(n->type != types[TVOID])
-				nullwarn(l, Z);
-			else
-				cgen(l, Z);
+			cgen(l, Z);
 			break;
 		}
 		/*