diff --git a/configure/CONFIG_COMMON b/configure/CONFIG_COMMON
index e40b70464..e3cf6c69f 100644
--- a/configure/CONFIG_COMMON
+++ b/configure/CONFIG_COMMON
@@ -99,8 +99,9 @@ GCC_SLIBS_YES =
 GCC_SLIBS_NO =
 GCC_CFLAGS_CROSS = -B$(GNU_LIB)/gcc-lib/ -nostdinc
 GCC_CPPFLAGS_CROSS = -nostdinc
-GCC_SHRLIB_CFLAGS_YES =  -fPIC -D_REENTRANT
+GCC_SHRLIB_CFLAGS_YES =  -fPIC
 GCC_SHRLIB_LDFLAGS_YES =  -shared
+GCC_POSIX_CPPFLAGS = -D_POSIX_C_SOURCE=199506L -D_POSIX_THREADS -D_REENTRANT
 
 G++ = $(GNU_BIN)/$(GNU_TARGET_PREFIX)cc$(CMPLR_SUFFIX)
 
@@ -120,8 +121,9 @@ G++_SFLAGS_NO =
 G++_SLIBS_YES =
 G++_SLIBS_NO =
 G++_DEPENDS_FLAG = -MM
-G++_SHRLIB_CFLAGS_YES =  -fPIC -D_REENTRANT
+G++_SHRLIB_CFLAGS_YES =  -fPIC
 G++_SHRLIB_LDFLAGS_YES =  -shared
+G++_POSIX_CPPFLAGS = -D_POSIX_C_SOURCE=199506L -D_POSIX_THREADS -D_REENTRANT
 
 #--------------------------------------------------
 # C compiler
@@ -216,10 +218,7 @@ INSTALL_DBDFLAGS = -I $(INSTALL_LOCATION)/dbd
 
 #--------------------------------------------------
 # POSIX flags
-#####POSIX = YES
-#####POSIX_FLAGS_YES = -D=_POSIX_C_SOURCE=199506L
-#####POSIX_FLAGS_NO = 
-#####POSIX_FLAGS = $(POSIX_FLAGS_$(POSIX))
+POSIX_CPPFLAGS = $($(ANSI)_POSIX_CPPFLAGS)
 
 #--------------------------------------------------
 # Warnings flags
@@ -275,7 +274,7 @@ LDFLAGS = $(OPT_LDFLAGS) $(TARGET_LDFLAGS) $(USR_LDFLAGS) $(DEPLIB_LDFLAGS)\
 LDLIBS = $(TARGET_LDLIBS) $(USR_LDLIBS) $(DEPLIB_LDLIBS) $(ARCH_DEP_LDLIBS)\
  $(STATIC_LDLIBS) $(OP_SYS_LDLIBS)
 
-CPPFLAGS += $(EPICS_BASE_CPPFLAGS) $(TARGET_CPPFLAGS) $(USR_CPPFLAGS) $(ARCH_DEP_CPPFLAGS)
+CPPFLAGS += $(POSIX_CPPFLAGS) $(EPICS_BASE_CPPFLAGS) $(TARGET_CPPFLAGS) $(USR_CPPFLAGS) $(ARCH_DEP_CPPFLAGS)
 
 CPPSNCFLAGS = $(INCLUDES)