diff --git a/devicemodel/Makefile b/devicemodel/Makefile
index 7335672161..1656ca1dcf 100644
--- a/devicemodel/Makefile
+++ b/devicemodel/Makefile
@@ -16,7 +16,7 @@ CFLAGS += -DNO_OPENSSL
 CFLAGS += -m64
 CFLAGS += -Wall -ffunction-sections
 CFLAGS += -Werror
-CFLAGS += -O2 -D_FORTIFY_SOURCE=2
+CFLAGS += -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2
 CFLAGS += -Wformat -Wformat-security -fno-strict-aliasing
 CFLAGS += -fpie
 
diff --git a/tools/acrn-crashlog/Makefile b/tools/acrn-crashlog/Makefile
index 3f74c99dc0..0534508855 100644
--- a/tools/acrn-crashlog/Makefile
+++ b/tools/acrn-crashlog/Makefile
@@ -18,7 +18,7 @@ CFLAGS += -D_GNU_SOURCE
 CFLAGS += -m64
 CFLAGS += -Wall -ffunction-sections
 CFLAGS += -Werror
-CFLAGS += -O2 -D_FORTIFY_SOURCE=2
+CFLAGS += -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2
 CFLAGS += -Wformat -Wformat-security -fno-strict-aliasing
 CFLAGS += -fpie
 CFLAGS += -Wall -Wextra -pedantic
diff --git a/tools/acrn-manager/Makefile b/tools/acrn-manager/Makefile
index 5342b2a329..2e3b9d9be2 100644
--- a/tools/acrn-manager/Makefile
+++ b/tools/acrn-manager/Makefile
@@ -9,7 +9,7 @@ MANAGER_CFLAGS += -DNO_OPENSSL
 MANAGER_CFLAGS += -m64
 MANAGER_CFLAGS += -Wall -ffunction-sections
 MANAGER_CFLAGS += -Werror
-MANAGER_CFLAGS += -O2 -D_FORTIFY_SOURCE=2
+MANAGER_CFLAGS += -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2
 MANAGER_CFLAGS += -Wformat -Wformat-security -fno-strict-aliasing
 MANAGER_CFLAGS += -fpie -fpic
 #FIXME: remove me. work-around for system() calls, which will be removed
diff --git a/tools/acrnlog/Makefile b/tools/acrnlog/Makefile
index 8c7a9ff1e6..749c20c2ca 100644
--- a/tools/acrnlog/Makefile
+++ b/tools/acrnlog/Makefile
@@ -8,7 +8,7 @@ LOG_CFLAGS += -DNO_OPENSSL
 LOG_CFLAGS += -m64
 LOG_CFLAGS += -Wall -ffunction-sections
 LOG_CFLAGS += -Werror
-LOG_CFLAGS += -O2 -D_FORTIFY_SOURCE=2
+LOG_CFLAGS += -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2
 LOG_CFLAGS += -Wformat -Wformat-security -fno-strict-aliasing
 LOG_CFLAGS += -fpie -fpic
 LOG_CFLAGS += $(CFLAGS)
diff --git a/tools/acrntrace/Makefile b/tools/acrntrace/Makefile
index fa42880a99..22ff4f9015 100644
--- a/tools/acrntrace/Makefile
+++ b/tools/acrntrace/Makefile
@@ -8,7 +8,7 @@ TRACE_CFLAGS += -DNO_OPENSSL
 TRACE_CFLAGS += -m64
 TRACE_CFLAGS += -Wall -ffunction-sections
 TRACE_CFLAGS += -Werror
-TRACE_CFLAGS += -O2 -D_FORTIFY_SOURCE=2
+TRACE_CFLAGS += -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2
 TRACE_CFLAGS += -Wformat -Wformat-security -fno-strict-aliasing
 TRACE_CFLAGS += -fpie -fpic
 TRACE_CFLAGS += $(CFLAGS)