Index: kernel/Makefile
===================================================================
--- kernel/Makefile	(revision 46577995860f76c247274a43eb6f67b944f0d3a8)
+++ kernel/Makefile	(revision e211ea04fccf33d4cb2092f630a29e893e096a02)
@@ -87,5 +87,5 @@
 INCLUDES_FLAGS = $(addprefix -I,$(INCLUDES))
 
-DEFS = -DKERNEL -DRELEASE=$(RELEASE) "-DCOPYRIGHT=$(COPYRIGHT)" "-DNAME=$(NAME)" -D__$(BITS)_BITS__ -D__$(ENDIANESS)__
+DEFS = -DKERNEL -DRELEASE=$(RELEASE) "-DCOPYRIGHT=$(COPYRIGHT)" "-DNAME=$(NAME)" -D__$(BITS)_BITS__ -D__$(ENDIANESS)__ -D__OPAQUE_ERRNO__
 
 COMMON_CFLAGS = $(INCLUDES_FLAGS) -O$(OPTIMIZATION) -imacros $(CONFIG_HEADER) \
Index: uspace/Makefile.common
===================================================================
--- uspace/Makefile.common	(revision 46577995860f76c247274a43eb6f67b944f0d3a8)
+++ uspace/Makefile.common	(revision e211ea04fccf33d4cb2092f630a29e893e096a02)
@@ -177,5 +177,6 @@
 	-ffreestanding -fno-builtin -nostdlib -nostdinc -fexec-charset=UTF-8 \
 	-finput-charset=UTF-8 -D__$(ENDIANESS)__ -fno-common \
-	-fdebug-prefix-map=$(realpath $(ROOT_PATH))=.
+	-fdebug-prefix-map=$(realpath $(ROOT_PATH))=. \
+	-D__OPAQUE_ERRNO__
 
 GCC_CFLAGS = -ffunction-sections -Wall -Wextra -Wno-clobbered \
Index: uspace/lib/c/generic/vfs/vfs.c
===================================================================
--- uspace/lib/c/generic/vfs/vfs.c	(revision 46577995860f76c247274a43eb6f67b944f0d3a8)
+++ uspace/lib/c/generic/vfs/vfs.c	(revision e211ea04fccf33d4cb2092f630a29e893e096a02)
@@ -1279,4 +1279,7 @@
 	async_wait_for(req, &rc_orig);
 
+	// XXX: Workaround for GCC diagnostics.
+	*handle = -1;
+
 	if (rc_orig != EOK)
 		return (errno_t) rc_orig;