diff --git a/require.Makefile b/require.Makefile
index db4f8bcd1e6647bbb6a2933b0418067097ccbc16..16d3c3face0e0a9bc23fc0009d47b0416836f5a1 100644
--- a/require.Makefile
+++ b/require.Makefile
@@ -67,7 +67,7 @@ HEADERS += $(APPSRC)/require.h
 #
 USR_INCLUDES_Linux=-idirafter $(EPICS_BASE)/include
 
-USR_CFLAGS += --std=c99
+USR_CFLAGS += -std=c99
 
 # ESS require doesn't use T_A, because Linux should handle linux as "1"
 # instead of its name. ESS require can handle them within the EPICS