Fix foward declaration duplication
diff --git a/include/grpc/impl/codegen/slice.h b/include/grpc/impl/codegen/slice.h
index ef60ce1..4d4a86f 100644
--- a/include/grpc/impl/codegen/slice.h
+++ b/include/grpc/impl/codegen/slice.h
@@ -37,7 +37,7 @@
 #include <stddef.h>
 #include <stdint.h>
 
-typedef struct grpc_exec_ctx grpc_exec_ctx;
+#include <grpc/impl/codegen/exec_ctx_fwd.h>
 
 /* Slice API