diff --git a/src/helper/Makefile.am b/src/helper/Makefile.am
index 0d886843c..c1aeebf00 100644
--- a/src/helper/Makefile.am
+++ b/src/helper/Makefile.am
@@ -30,12 +30,6 @@ noinst_LTLIBRARIES += %D%/libhelper.la
 	%D%/jep106.inc \
 	%D%/jim-nvp.h
 
-%C%_libhelper_la_CFLAGS = $(AM_CFLAGS)
-if IS_MINGW
-# FD_* macros are sloppy with their signs on MinGW32 platform
-%C%_libhelper_la_CFLAGS += -Wno-sign-compare
-endif
-
 STARTUP_TCL_SRCS += %D%/startup.tcl
 EXTRA_DIST += \
 	%D%/bin2char.sh \
diff --git a/src/rtos/Makefile.am b/src/rtos/Makefile.am
index 49cb830e5..f09ac21a2 100644
--- a/src/rtos/Makefile.am
+++ b/src/rtos/Makefile.am
@@ -31,10 +31,3 @@ noinst_LTLIBRARIES += %D%/librtos.la
 	%D%/rtos_riot_stackings.h \
 	%D%/rtos_ucos_iii_stackings.h \
 	%D%/nuttx_header.h
-
-%C%_librtos_la_CFLAGS = $(AM_CFLAGS)
-
-if IS_MINGW
-# FD_* macros are sloppy with their signs on MinGW32 platform
-%C%_librtos_la_CFLAGS += -Wno-sign-compare
-endif
diff --git a/src/server/Makefile.am b/src/server/Makefile.am
index 5f7469a84..fb5248bfd 100644
--- a/src/server/Makefile.am
+++ b/src/server/Makefile.am
@@ -14,10 +14,4 @@ noinst_LTLIBRARIES += %D%/libserver.la
 	%D%/ipdbg.c \
 	%D%/ipdbg.h
 
-%C%_libserver_la_CFLAGS = $(AM_CFLAGS)
-if IS_MINGW
-# FD_* macros are sloppy with their signs on MinGW32 platform
-%C%_libserver_la_CFLAGS += -Wno-sign-compare
-endif
-
 STARTUP_TCL_SRCS += %D%/startup.tcl