diff --git a/configure/os/CONFIG.Common.V69-ppc604 b/configure/os/CONFIG.Common.V69-ppc604
index afb6c03d6..b19505862 100644
--- a/configure/os/CONFIG.Common.V69-ppc604
+++ b/configure/os/CONFIG.Common.V69-ppc604
@@ -4,3 +4,6 @@ export LD_LIBRARY_PATH=$(WIND_BASE)/lmapi-5.0/$(WIND_HOST_TYPE)/lib
 
 # -fno-implicit-fp causes error: "unable to find a register to spill in class 'FLOAT_REGS'"
 ARCH_DEP_CFLAGS =  -mcpu=604 -mstrict-align
+
+# VxWorks 6.9.0 has buggy int8_t in stdint.h
+ARCH_DEP_CFLAGS += -fsigned-char