diff --git a/config/config.mk b/config/config.mk
index 4aeb2f73f39..16e9b8c645a 100644
--- a/config/config.mk
+++ b/config/config.mk
@@ -247,6 +247,7 @@ else # ! MOZ_DEBUG
 # Used in the Windows nightlies to generate symbols for crash reporting.
 ifdef MOZ_DEBUG_SYMBOLS
 OS_CXXFLAGS += -Zi -UDEBUG -DNDEBUG
+OS_CFLAGS += -Zi -UDEBUG -DNDEBUG
 OS_LDFLAGS += -DEBUG -OPT:REF -OPT:nowin98
 endif