diff --git a/src/cmd/gc/select.c b/src/cmd/gc/select.c
index 35da0557b6..d3c04c659e 100644
--- a/src/cmd/gc/select.c
+++ b/src/cmd/gc/select.c
@@ -214,6 +214,11 @@ walkselect(Node *sel)
 				n->left = nod(OADDR, n->left, N);
 				n->left->etype = 1;  // pointer does not escape
 				typecheck(&n->left, Erv);
+				if(!eqtype(ch->type->type, n->left->type->type)) {
+					n->left = nod(OCONVNOP, n->left, N);
+					n->left->type = ptrto(ch->type->type);
+					n->left->typecheck = 1;
+				}
 			} else {
 				tmp = temp(ch->type->type);
 				a = nod(OADDR, tmp, N);
@@ -330,6 +335,13 @@ walkselect(Node *sel)
 				n->right = nod(OADDR, n->right, N);
 				n->right->etype = 1;  // pointer does not escape
 				typecheck(&n->right, Erv);
+				// cast to appropriate type if necessary.
+				if(!eqtype(n->right->type->type, n->left->type->type) &&
+					assignop(n->right->type->type, n->left->type->type, nil) == OCONVNOP) {
+					n->right = nod(OCONVNOP, n->right, N);
+					n->right->type = ptrto(n->left->type->type);
+					n->right->typecheck = 1;
+				}
 				r->ntest = mkcall1(chanfn("selectsend", 2, n->left->type), types[TBOOL],
 					&r->ninit, var, n->left, n->right);
 				break;
diff --git a/test/fixedbugs/issue6847.go b/test/fixedbugs/issue6847.go
new file mode 100644
index 0000000000..e6427e19ac
--- /dev/null
+++ b/test/fixedbugs/issue6847.go
@@ -0,0 +1,85 @@
+// compile
+
+// Copyright 2014 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 6847: select clauses involving implicit conversion
+// of channels trigger a spurious typechecking error during walk.
+
+package p
+
+type I1 interface {
+	String()
+}
+type I2 interface {
+	String()
+}
+
+func F() {
+	var (
+		cr <-chan int
+		cs chan<- int
+		c  chan int
+
+		ccr chan (<-chan int)
+		ccs chan chan<- int
+		cc  chan chan int
+
+		ok bool
+	)
+	// Send cases.
+	select {
+	case ccr <- cr:
+	case ccr <- c:
+	}
+	select {
+	case ccs <- cs:
+	case ccs <- c:
+	}
+	select {
+	case ccr <- c:
+	default:
+	}
+	// Receive cases.
+	select {
+	case cr = <-cc:
+	case cs = <-cc:
+	case c = <-cc:
+	}
+	select {
+	case cr = <-cc:
+	default:
+	}
+	select {
+	case cr, ok = <-cc:
+	case cs, ok = <-cc:
+	case c = <-cc:
+	}
+      // Interfaces.
+	var (
+		c1 chan I1
+		c2 chan I2
+		x1 I1
+		x2 I2
+	)
+	select {
+	case c1 <- x1:
+	case c1 <- x2:
+	case c2 <- x1:
+	case c2 <- x2:
+	}
+	select {
+	case x1 = <-c1:
+	case x1 = <-c2:
+	case x2 = <-c1:
+	case x2 = <-c2:
+	}
+	select {
+	case x1, ok = <-c1:
+	case x1, ok = <-c2:
+	case x2, ok = <-c1:
+	case x2, ok = <-c2:
+	}
+	_ = ok
+}