diff --git a/mps/code/prmcfr.h b/mps/code/prmcfr.h
index 4abebe2c883..5514b683aca 100644
--- a/mps/code/prmcfr.h
+++ b/mps/code/prmcfr.h
@@ -11,7 +11,7 @@
 
 #include "mpm.h"
 
-#include <signal.h>
+#include <ucontext.h>
 
 typedef struct MutatorFaultContextStruct { /* Protection fault context data */
   ucontext_t *ucontext;
diff --git a/mps/code/protfri3.c b/mps/code/protfri3.c
index 0faf92ee19b..95408eae24b 100644
--- a/mps/code/protfri3.c
+++ b/mps/code/protfri3.c
@@ -26,6 +26,8 @@
 #include <signal.h>
 #include <machine/trap.h>
 
+#include <stdlib.h>     /* for abort */
+
 SRCID(protfri3, "$Id$");