diff --git a/Makefile-gcc b/Makefile-gcc
index 766b0c9bb..b8f1f530f 100644
--- a/Makefile-gcc
+++ b/Makefile-gcc
@@ -37,6 +37,7 @@ CFLAGS := -Ipub -Ipriv \
 	-Wcast-align -Wmissing-declarations \
 	-Wwrite-strings -Wformat -Wformat-security \
 	-std=gnu99 -fstrict-aliasing -fPIC \
+	-DPYVEX \
 	$(EXTRA_CFLAGS)
 
 # If not debugging, put -g -O2 after any flags we inherit from our invoker
diff --git a/Makefile-msvc b/Makefile-msvc
index 2ff781120..a58271a72 100644
--- a/Makefile-msvc
+++ b/Makefile-msvc
@@ -19,7 +19,7 @@ STATIC_LIBRARY_FILE = libvex.lib
 DYNAMIC_LIBRARY_FILE = libvex.dll
 EXTRA_CLEAN_FILES = auxprogs/genoffsets.exe genoffsets.obj
 
-CCFLAGS = /Ipub /Ipriv $(EXTRA_CFLAGS) /O2 /wd4715
+CCFLAGS = /Ipub /Ipriv $(EXTRA_CFLAGS) /O2 /wd4715 /DPYVEX
 
 all: vex
 
diff --git a/priv/main_main.c b/priv/main_main.c
index 0e394e104..4b8e090ef 100644
--- a/priv/main_main.c
+++ b/priv/main_main.c
@@ -384,6 +384,11 @@ IRSB *LibVEX_Lift (  VexTranslateArgs *vta,
    if (vta->arch_host == VexArchS390X) {
       s390_host_hwcaps = vta->archinfo_host.hwcaps;
    }
+#ifdef PYVEX
+   if (vta->arch_guest == VexArchS390X) {
+      s390_host_hwcaps |= VEX_HWCAPS_S390X_LDISP | VEX_HWCAPS_S390X_VX;
+   }
+#endif
 
    /* First off, check that the guest and host insn sets
       are supported. */