diff --git a/BaseTools/Source/C/VfrCompile/Pccts/antlr/makefile b/BaseTools/Source/C/VfrCompile/Pccts/antlr/makefile
index 746d58b5e2..b47c8a37af 100644
--- a/BaseTools/Source/C/VfrCompile/Pccts/antlr/makefile
+++ b/BaseTools/Source/C/VfrCompile/Pccts/antlr/makefile
@@ -169,7 +169,7 @@ ANTLR=${BIN_DIR}/antlr
 DLG=${BIN_DIR}/dlg
 OBJ_EXT=o
 OUT_OBJ = -o
-CFLAGS= $(COPT) -I. -I$(SET) -I$(PCCTS_H) -DUSER_ZZSYN $(COTHER) -DZZLEXBUFSIZE=65536
+CFLAGS= $(COPT) -I. -I$(SET) -I$(PCCTS_H) -DUSER_ZZSYN $(COTHER) -DZZLEXBUFSIZE=65536 -std=gnu11
 CPPFLAGS=
 #
 # SGI Users, use this CFLAGS
diff --git a/BaseTools/Source/C/VfrCompile/Pccts/dlg/makefile b/BaseTools/Source/C/VfrCompile/Pccts/dlg/makefile
index e45ac98e04..d72bee3d70 100644
--- a/BaseTools/Source/C/VfrCompile/Pccts/dlg/makefile
+++ b/BaseTools/Source/C/VfrCompile/Pccts/dlg/makefile
@@ -123,7 +123,7 @@ endif
 COPT=-O
 ANTLR=${BIN_DIR}/antlr
 DLG=${BIN_DIR}/dlg
-CFLAGS= $(COPT) -I. -I$(SET) -I$(PCCTS_H) -DUSER_ZZSYN -DZZLEXBUFSIZE=65536
+CFLAGS= $(COPT) -I. -I$(SET) -I$(PCCTS_H) -DUSER_ZZSYN -DZZLEXBUFSIZE=65536 -std=gnu11
 CPPFLAGS=
 OBJ_EXT=o
 OUT_OBJ = -o